Tag Archives: Paintings

Plant Families: Araceae (aka Aroids or Arums)

Zantedeschia Inflorescence

Zantedeschia Inflorescence

A Few Basic Facts

  • Aroids are monocots in the family Araceae (aka arum family), in the order Alismatales. Most other families in this order contain tropical or aquatic plants, eg Hydrocharis and Saggitaria.
  • Araceae has 104-107 genera. The largest genus is Anthurium with over 700 species.
  • Location: Latin American tropical regions have the greatest diversity of aroids, however, they can also be found in Asia and Europe. Australia has only one endemic species – Gymnostachys.
  • Habitat: Aroids can be aquatic (water), epiphytic (air) and terrestrial (ground). Most are tropical, but there are also arid and cold loving aroids.
  • Distinctive features: All have an inflorescence (a structure containing a group of smaller flowers) which consists of a spadix (always) and a spathe (sometimes).
OLYMPUS DIGITAL CAMERA

Aroid Flowers

  • Aroids can be hermaphrodite (each flower is both male and female), monoecious (male and female flowers on the same spadix) or dioecious (male and female flowers on completely different plants).
  • This family contains one of the largest flowers (Amorphophallus titanium, the titan arum) and the smallest (Wolffia, duckweed).
  • Some aroid leaf and inflorescence shapes:
Aroid Leaf Shapes

Aroid Leaf Shapes

Leaves

Aroid Leaves

Fruits

Aroid Fruits

Adaptations

Like many tropical families, aroids have evolved a number of adaptations to stay healthy and propagate. Some examples of adaptation:

  • The spathe protects the flowers and in some cases is used to trap insects for pollination. It is not a petal, but a modified leaf. Many spathes turn green and photosynthesize after flowering has finished.
  • Aroids have different types of roots adapted to their purpose. They have different adventitious roots  for climbing, attaching to rocks or taking in water.
  • Many tropical species have shiny leaves to deter the mosses and lichens that grow in abundance in the rainforest.
  • Smell is used by many species to attract pollinators. The smell of rotting meat, fungi and excrement is used for flies and beetles. Fragrant scents are used to attract bees.
  • In many species the spadix actually heats up and can reach 25°C, even in near freezing conditions. This increases the release of smells to attract pollinators. The heat also makes visiting insects more active.
  • Aroids that want to attract flies and beetles often have a warty, hairy, twisted appearance, with dark colours. This is to mimic the effect of dead animals, fungi or excrement.
  • In some species, leaves may change shape from juvenility to adulthood – changing from variegated to unvariegated, pale red to green, or altering the number of lobes of the leaf. Colour change may deter animals from feasting on the fresh young leaves by making them look less leaf-like.
  • Most species in Araceae have tubers or rhizomes, this means a damaged plant has the food storage and ability to grow new shoots from many points beneath the ground. Some aroids have other means of vegetatively propagating themselves, such as bubils and offsets.
  • A number of aroids are poisonous, some are edible. Aroids have evolved poisons in some species as protection. Those that are edible did not evolve to be eaten by us, rather we have evolved to be able to eat certain plants.

Reproduction

IMG_4023

Male and Female Flowers

Because many aroids are monoecious there is a danger of self-pollination. While self-pollination is easy (a guaranteed fertilisation), it leads to less genetic variety and less ability to adapt to changes in the environment. Aroids are particularly variable plants, in one small area of the Thai Peninsula 22 distinct varieties of the plant Aglaonaemia nitidum f. curtisii were found. However, in order to achieve this variation, the plant needs to cross pollinate reliably. It does this by being protogynous, meaning the female flowers on an inflorescence ripen first and then later male flowers produce pollen.

The Generic Process for Monoecious Aroids

A beetle, fly or bee (hopefully covered in pollen) is attracted by the scent given off by the heated spadix. The insect flies around inside the spathe, lands on the slippery surface and falls into the gap between the spadix and spathe. At this point only the female flowers are mature, and the  insect, made more active by heat from the spadix, moves about bumping into the flowers and depositing the pollen. Now, the insect has fulfilled the first part of its function, the aroid would like it to pick up pollen from the male flowers. However, the male flowers will not ripen for a day or so yet, so the insect needs to be held hostage. The slippery spathe ensures that the insect can’t escape, it is given sustenance in the form of nectar. Once the male flowers are ready and producing pollen, the slippery surface of the spathe breaks down, allowing the insect to escape. As it flies away it bumps into the male flowers, picking up more pollen to take to the next plant of the same species that it comes to.

Two Specific Examples of Monoecious Reproduction

Philodendron auminatissimum: Sometimes the pollinating insect can outstay its welcome, perhaps damaging flowers or laying eggs. This Philodendron has overcome the problem by shrinking the spathe after the male flowers have become active. This means that the beetle must leave or become crushed.

Arum nigrum: This arum doesn’t trap visiting flies, it merely confuses them. The hood of the spathe hangs over the spadix, obscuring the  sunlight, and there are translucent marking in the base of the spathe. When a visiting fly tries to escape, it heads for the light, but this just guides it deeper into the spathe. This leads to panicked and more active movement, ensuring pollination.

Arum nigrum

Arum nigrum

Reproduction in Other Aroids

In dioecious aroids the female flowers are found on a different plant to the male flowers, so a genetic mix is guaranteed. Not many aroids are dioecious, but a few species of Arisaema are.

A few aroids are even paradioecious and change gender to suit circumstances.

Hermaphrodite aroids are similar to monoecious ones, the male and female parts on each flower mature at different times so self pollination cannot occur.

Habitat

Arid

For the most part, arid aroids have not evolved the typical shrunken leaves and thickened cuticle of other desert plants. Instead they tend to grow under trees and bushes and at the base of rocks where a damp, shady microclimate allows them to survive. They have unusually lush foliage for arid plants. This would make them a target for being eaten, but they have dealt with this by producing harsh toxins and needles of calcium oxalate that pierce and poison the throats of animals. Animals know to stay well clear of aroids.

Some Examples

Dead Horse Arum

Heliocodicerous muscivorus

Heliocodicerous muscivorus: This is called the dead horse arum. It has an inflorescence 35cm long and wide. It grows in the shelter of rocks on a few islands on the Mediterranean. It is pollinated by either flies or beetles and grows where sea birds have their colonies at nesting time. Sea birds live in a mess of rotting fish and eggs, dead chicks and excrement, which attracts the flies/beetles. The arum must then compete with the smell of these, in order to attract those same insects for pollination. It mimics the dead not only in smell, but also by looking like the corpse of part of a horse, complete with tail. Visiting insects find themselves falling into where the ‘tail’ is and becoming trapped by the slippery walls. Many insects lay their eggs inside, although any maggots that hatch will likely starve to death. The insects are held for two to three days and are fed by nectar.

Note: It’s worth looking at photos of the dead horse arum, my painting doesn’t really do it justice.

Sauromatum venosum: This is the called the voodoo lily because it has the ability to flower without soil or water, using only the energy stored as starch in the corm. It smells rotten.

Stylochaeton lancifolius: This aroid has flowers and fruits half buried in the ground. I have been unable to find information about why this is. My suspicions are:

  1.  It is pollinated by animals that are close to the ground. This can be seen in Aspidistra flowers, pollinated by slugs and snails. The flowers grow on the ground, under the leaves.
  2. Being submerged provides a little protection, even if eaten or stepped on, the Stylochaeton still has half a flower remaining.
  3. The fruits are eaten by something small. Having eaten the fruit, the seeds can be dispersed in the faeces.
Stylochaeton lancifolia

Stylochaeton lancifolia

Tropical

2346

Rainforests are dense, shady, and teeming with aggressive life. Animals, plants, fungi and bacteria are locked in a constant arms race. Consequently aroids have developed strong poisons, shiny leaves and the ability to climb to cope with some of these problems. In the tropics, latitudinal diversity (a wider variety of organisms that occurs close to the equator) means that it may be many miles through dense forest between plants of the same species. For this reason, aroids use very strong, and often unpleasant, smells to attract the right kind of insect.

A tropical rainforest has distinct layers and aroids grow in each of these. There are terrestrial aroids growing in the ground and epiphytic ones that climb into the canopy.

Climbers and epiphytes have only aerial, adventitious roots. There are two types: those that are sensitive to light and make for dark crevices where they can grip, and those that are sensitive to gravity and hang down from the plant in order to soak up rain and humidity.

Terrestrial Examples

Deiffenbachia grows in the Americas, while Aglaonema is native to Asia, they are both highly variable, but virtually indistinguishable from one another. This is an example of convergent evolution. Both contain toxins as a defence; Deiffenbachia is commonly known as dumb cane, because the if eaten, it causes the throat to swell, so that speech is impossible.

Ag 2

Aglaonema and Deiffenbachia – both highly variable, but in similar ways

 

Amorphophallus: This is a genus of tropical and subtropical aroids, native to Asia, Africa and Australasia. They attract flies and beetles by giving off the smell of rotting meat. Unusually, Amorphophallus species only put out one leaf or one inflorescence at a time, one a year. The single leaf is highly divided.

IMG_4021

Some Amorphophallus inflorescences

IMG_0352

Single, highly divided leaf of Amorphophallus

Some species in this genus also have white patches on the stem, these are to mimic lichen growing on trees and serve to protect them from stampeding elephants. When tramping through the jungle elephants have learnt to avoid trees, which are usually covered in lichen. Amorphophallus would be very easily damaged by an elephant, so by looking a bit more like a tree they can fool the elephant into avoiding them.

IMG_0357

Lichen mimicking stem

Epiphytic Examples

IMG_0770

Monstera

Monstera: These are one of the few plants to have holes in their leaves. Recent research shows that leaves with holes benefit in shady areas because the light coming through the trees is often dappled. By having holes in their leaves, Monstera cover a larger area with the same amount of leaf (so the same amount of energy used to make it) as a smaller leaf without holes. This allows the plant to take advantage of any sunlight that gets through the canopy.

Anthurium punctatum: This is an aroid from Ecuador. It has formed a symbiotic relationship with ants. It has nectaries away from the flowers because it is not trying to attract pollinators, but protectors. The ants set up home in the Anthurium and guard it from animals and insects that may eat it. However, in this Anthurium the ants are particularly aggressive and keep away pollinators also. The ants also secrete an antibiotic substance called myrmiacin, which is antibiotic and protects the ants from moulds and bacteria that might cause disease. However, this substance prevents pollen tube formation needed for the plant to be fertilised. These two barriers to pollination mean that the species can only propagate itself vegetatively.

Philodendron: This is a diverse genus. Plants can be epiphytic, hemiephytic or (occasionally) terrestrial. Hemiepiphytic means that the plant spends part of its life-cycle as an epiphyte (in the air). It may start off on the ground and then wind its way up a tree, then let its original roots die back. Or it may start as a seedling in the branches of a tree and a root will trail its way to the ground.

Philodendron bipinnatifidum

Philodendron bipinnatifidum

Temperate Woodland

Arisarum proboscideum

Arisarum proboscideum

Arisarum proboscideum: aka the mouse plant. This is a woodland aroid, native to Spain and Italy. It has flowers like little mice. The ‘tails’ of these give off a mushroomy odor, that attract fungus gnats for pollination. The flowers have a spongy white appendage inside the spadix that looks like a mushroom to complete the deception. Fungus gnats often lay their eggs in the flowers, although the maggots won’t live to adulthood.

Aquatic

As I have blogged before, plants never evolved much in water. This means that all aquatic plants have evolved on land and then evolved again to cope with life in water. Some problems faced are – damage to flowers and leaves due to water currents, lack of access to pollinators, water blocking out light, lack of oxygen (leading to rotting roots), and the heaviness of water (800 times as dense as air) putting pressure on foliage.

Some solutions to problems:

  • Aerenchyma:  these are gas filled cavities that improve buoyancy and oxygenation.
  • Fish shaped foliage: these offer less resistance to water currents, so less damage occurs.
  • Larger surface area in relation to volume: ie filmy leaves. This increases photosynthesis  eg Cryptocoryne
  • Roots: These are not needed to transport water, since it can be taken in by all parts of the plant. However, roots are used to anchor the plant and stopped it being carried away by currents. eg Jasarum steyermarkii
  • Reproduction: Many aquatic aroids find it easier to spread vegetatively rather than by flowering, in order to avoid flowering problems.

An Example

Pistia stratiotes 2.JPG

Pistia stratiotes: This is the only floating aquatic aroid, growing in swampy deltas in India and West Africa. It is adapted to staying still in fast moving currents, and has found the balance between sinking and blowing away.  The inner tissues have aerenchyma and the outer surfaces are ridged, velvety and with dense covering of hairs. This makes it unable to sink, and water repellent. Feathery roots act as an anchor. It has tiny flowers in a protective hairy spathe.

Pistias form a dense mat on the surface of the water, and can create mats of 15m wide. This makes Pistia something of a weed, causing problems to the ecosystem because the water underneath is deprived of light.

However, Pistia is not only harmful, some ecological benefits:

  • The darkness caused by the Pistia mats has led to the evolution of blind elephantnose fish, which live beneath the mats. They hunt by electricity and have well developed brains and learning abilities.
  • Birds and animals often make the floating island their home.
  • Pistia can purify stagnant water.

 

Note: outdoor photos are mostly taken in Ecuador and indoor photos mostly from Wisley Gardens.

 

Plant Divisions: Cycads

Cycas

Cycas

Cycadophyta is a plant division that contains only trees, the cycads, which are palm-like gymnosperms. They first appear in the fossil record 280mya and haven’t changed much since then, although a fair few genera became extinct 200mya.

Cycads have long, narrow leaves, with either pinnate or bipinnate leaflets forming in a whorl at the top of a trunk or growing on slender stems from the ground. They vary greatly in size, with some reaching 18m high while others are only 30cm. Cycad leaves often unfurl as they grow and as lower leaves die their bases remain attached to the stem to form an armour-like casing. Like all gymnosperms, cycads do not produce flowers or fruits, instead they reproduce by cones.

Cycads appear in a geographical band that stretches from the Tropic of Cancer to the Tropic of Capricorn. They are mostly found in tropical and subtropical regions in both the northern and southern hemispheres, for example Central and South America. They can live up to a thousand years, but tend to grow very slowly.

Leaves

Leaves of Zamia furfuracea

Leaves of Zamia furfuracea

All cycads are evergreens, with stiff long leaves. Many are pinnate (opposite leaflets along a central stem) or bipinnate (each pinnate leaflet divided into further leaflets). There is a little variety in the leaves of cycads, adult leaves can be blue-grey or green and they may be twisted or spiky. The veins in cycad leaves run in parallel lines from the leaf stem. Young leaves may be copper-coloured and in some genera they unfurl like fern leaves. Many cycads have stipules, these are small outgrowths at the base of the main leaf and can be useful in identification of plants. In general stipules can have different forms such as glands, hairs, miniature leaves, spines or scales, but on cycads they take the form of stunted leaf-like structures. In Bowenia and Stangeria the stipules are larger and fleshy, and their function is to protect the leaves as they grow.

Unfurling leaves of Cycas rumphii

Unfurling leaves of Cycas rumphii

Trunk and roots

Trunk of Encephalartos ferox

Trunk of Encephalartos ferox

Cycad stems are often thick, but are not true wood, instead they are fibrous and contain a lot of starch. Many cycads, for example Bowenia and Stangeria, have subterranean stems, these are carrot-like. Cycads also have specialised roots, termed collaroid roots, that form into coral like structures. Coralloid roots contain blue green algae that form a symbiotic relationship with the plant, fixing nitrogen for it.

Subterranean Stem of Cycas

Subterranean Stem of Cycas

Reproduction

Cones of Dioon and Ceratozamia

Cones of Dioon and Ceratozamia

It has recently been confirmed that cycads are pollinated by insects, which is rare for gymnosperms, but a distinct advantage for a plant that grows in tropical forests where there is little wind.

Cycads are dioecious which means that there are separate male and female plants, however cycads are one of the few plant groups that can change their gender, seemingly in response to stress such as physical damage or extreme cold. Plants are not as gender specific as mammals, (most are hermaphrodites) and although x and y chromosomes (the ones that differentiate gender) have been found in a few plants, the significance of these chromosomes in plants is still not fully understood.

Seeds with Red Sarcotesta in  Female Zamia loddigesii Cone

Seeds with Red Sarcotesta in Female Zamia loddigesii Cone

When cycads are not changing gender, the process of reproduction is very similar to that of conifers, the male cones release pollen, the female cones receive the pollen and form seeds. However, being dioecious, the male and female cones do not appear on the same tree as they do with conifers. On many cycad genera, the seeds that form have brightly coloured seed coats called sarcotestae (sarcotesta singular). This is slightly fleshy and edible to birds and animals which aids in the spreading of seed and is a forerunner to fruit. (This can be seen in the picture to the right, with the red seeds forming beneath the brown scales, pushing them out as the seeds enlarge) Pomegranates and Ginkgos also have sarcotestae.

Male Cones of Ceratozamia,, Chigua and Cycas

Male Cones of Ceratozamia, Chigua and Cycas

What is the difference between Cycads, Tree Ferns and Palms?

Cycads, tree ferns and palms can all easily get confused, all may have a central trunk, usually without side branches, and then a whorl of leaves at the top, consisting of a central rachis (the middle part of the leaf) with leaflets either side. All grow mainly in the tropics, although tree ferns can grow in more temperate areas too. However, the three types of trees are not closely related at all, each is in a different division, this can be seen most clearly in their very different ways of reproducing.

Palm Tree, Cycad, Tree Fern

Palm Tree, Cycad, Tree Fern

Cycads – Cycadophyta Division – reproduce by pollen, cones and seeds.

Tree ferns – Pteridophyta Division – reproduce by spores and have separate sporophyte and gametophyte generations. Leaves are divided into distinctive fern leaf shapes. Trunks tend to have leaf bases still attached, same as with cycads, and their trunks are also not true trunks, however tree fern trunks are made of modified roots.

Palms – Magnoliophyta Division – reproduce with flowers and fruits. Palms are more varied than cycads and may have palmate or fan leaves, or a trunk with spikes or smooth bark.

Cycadophyta Family Tree

Cycadophyta Family tree

Cycadophyta Family tree

Cycadophyta is a small division with only three families and eleven genera. A number of genera are now extinct, for example Beania and Crossozamia.

Zamiaceae

Zamiaceae

Zamiaceae – Zamia pseudomonticola, Dioon purpusii, Encephalartos horridus

This is the family with the most genera – Chigua, Zamia, Ceratozamia, Macrozamia, Lepidozamia, Dioon, Encephalartos, Microcycas – and consequently the widest variety of shapes. The sarcotesta in this family are red, yellow or brown.

Zamia pygmaea is the smallest cycad and, at 30cm, is in fact the smallest gymnosperm.

Some species of Macrozamia have leaves so fine they look almost like pine needles or grass, whereas Zamia have wider leaves. Encephalartos has some species with distinctive spiky leaf shapes (see photo).

Ceratozamia with Female Cone

Ceratozamia with Female Cone

 Cycadaceae

Cycadaceae - Cycas seemannii

Cycadaceae – Cycas seemannii

Mature Female Cycas cone with seeds forming

Mature Female Cycas cone with seeds forming

Cycadaceae contains only one genus Cycas. Although Cycas has many species, there is little variation in appearance, with all species having a stout trunk and a whorl of leaves at the crown. Cycas have notably different female cones to other cycads. The scales of the cones are open with seeds forming in between the scales, rather than underneath as in other cycads. The young leaves of Cycas are coiled (see near top for photo of unfurling leaves).

Stangeraceae

Stangeraceae - Stangeria eriopus

Stangeraceae – Stangeria eriopus

Stangeriaceae contains two genera, Bowenia and Stangeria. In this family, young leaves are coiled or folded. Stipules are present and the sarcotesta is purple. Most plants in this family have wider leaves than other cycads, although Stangeria paradoxa has leaflets as finely divided as a fern. Both genera have slender stems, with the trunk underground.

Bowenia spectabilis

Bowenia spectabilis

Plant Divisions: Mosses, Liverworts and Hornworts

Moss, Liverwort, Hornwort

Bryophytes used to be a general term for mosses, liverworts and hornworts, and these three were grouped together into a single division due to their similarity. It is now known that they are not closely related and they have been split into three separate divisions.

  • Bryophyta Division – mosses

  • Anthocerophyta Division – hornworts

  • Marchantiophyta Division – liverworts

Although the term bryophyte is still used to mean plants in all three divisions, including Bryophyta, I think that is confusing, so instead I will use “BAMs” (Bryophyta, Anthocerophyta and Marchantiophyta) to refer to the three divisions, and the plants within them.

Mosses

Moss

Introduction

BAMs (Bryophyta, Anthocerophyta and Marchantiophyta) were some of the earliest plants to evolve, as a result they are primitive when compared to later, vascular plants. Their leaves, stems, and the rhizoids they have in the place of roots, are all simpler and less effective. BAMs are non-vascular, although they do have a simple, conducting system for transporting water and nutrients, it does not contain the xylem and phloem vessels found in vascular plants and is not nearly so efficient. As a result, BAMs do not grow large, because they cannot transport water a long distance, and are limited to damp shady areas, because in the sun  they dry out. They reproduce by spores, rather than seeds and their reproductive cycle involves two distinct, external stages, (essentially two different plants) which does not happen in plants with seeds.

Acrocarp and PleurocarpMosses can be divided into two different groups:

  • Acrocarp – upright
  • Pleurocarp – creeping


Leafy and Thallose

Leafy and Thallose

And Liverworts:

  • Thallose – larger rubbery leaves and flower-like capsules containing spores (sporophytes). Thallose means the tissue is undifferentiated.
  • Leafy – smaller leaves arranged along a short stem, small globe capsules. Most liverworts are leafy.

The Hornwort Division is much smaller and does not split readily into types.

Note: Plants in the Ceratophyllum genus are also referred to as hornworts, these are very different plants and they are aquatic and flowering.

Moss with Sporophytes (capsules and seta)

Moss with Sporophytes (capsules and seta)

What makes BAMs different from other plants?

Click for close up

Click for close up

Roots and rhizoids: BAMs do not have roots, they have rhizoids, these are also found on horsetails and ferns (Pteridophyta), club mosses and quillworts (Lycopodiophyta). Some fungi and algae also have rhizoids. Rhizoids are similar to roots, in that they transport water and nutrients, and anchor the plant to the soil or substrate, but are much simpler in form, often only one cell thick.

Click for close up

Click for close up

Simple and Complex Leaves: Leaves on BAMs are single celled, apart from the midrib. They contain chloroplasts for photosynthesis, but otherwise the cells are not specialised as they are in other plants.

Reproduction

To explain how sexual reproduction is different in BAMs, it’s necessary to first explain sexual reproduction as it is in all organisms.

Diploid and Haploid Cells

Diploid and Haploid Cells

There are two types of cell:

  • Diploid cell (2n) –  a cell with two sets of DNA, most cells in an organism are diploid.
  • Haploid Cell (n) –  cell with one set of DNA, cells are only haploid when an organism is reproducing or preparing to reproduce.

And two types of cell division:

  • Mitosis – a cell replicates its DNA and splits in two so that each new cell has the same amount of DNA as the original. This type of cell division is used when an organism grows. Can occur in both haploid and diploid cells.
  • Meiosis – the DNA does not replicate and when the cell splits in two each new cell has half the DNA of the original. This type of cell division is used only for sexual reproduction. Occurs only in diploid cells and results only in haploid cells.*

Diagram Showing Mitosis

Diagram Showing Meiosis

Example: Daisy

Inside the flower of a daisy, some cells are dividing by meiosis in order to create haploid cells, called the male gamete. These haploid cells form pollen (each pollen grain contains one gamete) which are picked up by bees and deposited onto another daisy flower that will contain the female gamete. The two haploid gamete cells fuse to form a single diploid cell (one strand of DNA from each gamete), called the zygote. The zygote grows by mitosis in the flower until it forms a slightly larger and more complex embryo daisy. This embryo is contained within a seed which falls (or is blown) away from the mother plant to land and grow, by mitosis, into a new daisy, similar but not identical to the two parents.

This process is fairly similar in animals with the same use of meiosis and haploid cells to reproduce, the main difference is in how the male gamete finds the female gamete (eg by mating) and instead of falling as a seed the embryo is released as an egg, a pupa or forms inside the adult.

Diagram of Moss

Diagram of Moss

BAMs do not reproduce in quite the same way. Although they too create haploid cells by meiosis (called spores), these haploid cells form a plant called a gametophyte. The gametophyte is made of haploid cells and creates more haploid cells, the gametes, by mitosis. Some gametes are male, some female (although some species produce only male or female gametes and these gametes will need to find a gamete of the opposite gender to fuse with). A female gamete fuses with a male gamete to create a new diploid plant, called a sporophyte. Often the sporophyte grows out of the gametophyte (seen right). The sporophyte produces spores, these are haploid and each will potentially grow into a new gametophyte and so the cycle starts again.

This alternation of diploid and haploid plants, sporophyte and gametophyte, is called Alternation of Generations. It is often described as happening in all plants, but only plants, never animals (although it can also be said to happen in fungi). However, animals do have a diploid and haploid phase, the only real difference is that plant gametes, such as pollen can divide, whereas haploid gamete cells in animals cannot. Otherwise the process is very similar: diploid cells divide by meiosis to become haploid gametes and two gametes of different genders fuse to become a diploid zygote which then divides by mitosis to get bigger and become a whole new organism. Thank you to Walter Hintz at this website for helping me understand this http://www.allexperts.com/user.cgi?m=4&expID=48818&catID=664

Here are my question and his answer.

http://en.allexperts.com/q/Biology-664/2013/3/alternating-generations.htm

What makes BAMs different from each other?

Yellow Moss

Yellow Moss

All BAMs like moist shady areas, but mosses are a little hardier than liverworts and cope better with dry weather.

There are 12,000 species of moss, 6,000-8,000 species of liverwort but only 100 species of hornwort. Mosses are abundant in England, liverworts are a little harder to find and hornworts are not common here, preferring tropical climates.

Liverwort and Pencil Tip

Liverwort and Pencil Tip

I took a recent trip to Highgate Cemetery to find mosses and liverworts. I found a few liverworts in the really boggy areas, growing on soil, although liverworts can grow on stone. I was surprised at how small the liverworts were and the photo above shows some with a pencil tip to show size. Moss covered everything, but at first it was difficult to see any more than one kind – partly because I wasn’t used to looking and partly because certain mosses are much more successful than others and tend to take over. In the end I did spot a few different kinds, the photos throughout this blog are ones I took on the trip, but here are some close up photos of the different types of moss I discovered.

Mosses Found In Highgate Cemetery

Mosses Found In Highgate Cemetery

Differences in Appearance

Liverwort

Liverwort

Mosses are soft and leafy, with many tiny leaves, and the sporophytes are small capsules on the end of long thin seta (seen in diagrams above). Liverworts have slightly larger, flat rubbery leaves usually growing much closer to the ground, their sporophytes are either like rubbery, green flowers (seen on the drawing at the top of this page) or globes on a stem (seen below). Some liverworts have round gemma cups (seen at the top of this photo) containing fragments of liverwort that can break away and form new gametophytes, this is a form of asexual reproduction. Gemmae can also be found in mosses. Hornworts look fairly similar to liverworts in the gametophyte stage, but the sporophyte is a distinctive long, thin, needle-like protuberance.

Liverwort with Sporophytes

Liverwort with Sporophytes

Differences in Biology

The biological differences are a little detailed for the purposes of this blog, so I will only list a few briefly: Hornworts produce slime in between the cells. Most hornwort species have a single chloroplast in each cell, unlike liverworts, mosses and all other plants, only algae have this same feature. The rhizoids in mosses are multicellular, but unicellular in hornworts and liverworts. Mosses and hornworts have true stomata (breathing holes) on their sporophytes, but liverworts do not.

Bizarre bryophytes and not-bryophytes

Spanish Moss

Spanish Moss

Spanish moss or beard lichen is often thought to be a parasitic, but it merely grows in abundance on trees. However, it is NOT actually a moss, or a lichen, but a flowering plant in the bromeliad family. Ball moss is similar, a flowering plant rather than a moss. Reindeer moss is also not a moss, but a lichen.

This picture was taken from the following website http://www.learnnc.org/lp/multimedia/6540

Mosses are not parasitic, but some liverworts are. Aneura mirabilis, Cryptothallus mirabilis and Cryptothallus hirsutus are all parasitic liverworts. They are pale because they have no chlorophyll and therefore cannot photosynthesize. Instead they gain their nutrients from fungi that are working symbiotically with a tree, ie the fungus and tree are aiding one another, the tree provides carbohydrate for the fungus, the fungus extracts nutrients from the soil for the tree and then the Aneura sneaks in and takes nutrients from the fungus without giving anything back.

Luminous Moss

Luminous Moss

Luminous moss (Schistostega pennata), also known as Elfin Gold, glows green in the dark. It can take light, no matter how faint, and reflect it, leading to the luminescence. For this reason it is able to grow in places too dark for other mosses. It is native to the Northern Hemisphere and is found growing in caves or between rocks. This picture is taken from http://www.botanic.jp/plants-ha/higoke.htm and there are other pictures of the moss on that site.

*Note to meiosis: Occasionally, or with some specific species, the process of meiosis and mitosis do not occur as described above, and instead a cell, a tissue, or an entire organism can end up having more than two sets of DNA. For example if a diploid cell does not split by meiosis as usual and then fuses with a haploid cell, the result is a cell with three sets of chromosomes. This state is called polyploidy, it can have a function, both biologically and commercially.