Fungi

Fungi represent a very important part of the thallophytes and are separated from the rest by many definite characteristics. They have no chlorophyll and no starch is present in their cells and it is easy to see from the example of a few familiar toadstools that they are quite different in actual make-up from all other plants. They do not live on their own manufactured food, but rely either on the decaying remains of other plants and animal life(these types are called saprophytes)or on living plants or animals(parasites). The fungi may be single celled plants such as yeast, which is used for baking bread and brewing beer, or multi-celled plants such as the mushroom. In these more advanced forms the main part of the plant is an intricate web of threads known as hyphae, the whole web being called the mycelium. This often lives underground or inside the host plant on which the fungus is living. The hyphae threads run about either in or between the cells of the plant and have the power of dissolving the cellulose of the cell walls and living on the contents. The saprophytic ones act in a similar way on dead organic material and are not generally harmful to plants or animals. These parasites on the other hand cause man a great deal of trouble and expense in trying to get rid of them. Some fungi attack animals, including man, an example being the fungal disease athlete's foot. With the larger fungi, the hyphae sometimes come above ground and form a special structure which can produce spores. This is the fruiting stage of the plant and the mushroom and toadstool are examples of this. The hyphae have another property which is important to the fungus and this is the formation of a hard tuber like body called sclerotium(again a resting stage) which is capable of existing for a long time without actually growing, or doing damage in the case of harmful fungi. This stage makes it difficult to get rid of some fungal diseases for they can withstand a lot of adverse treatment, and then germinate when conditions are suitable. As fungi lack chlorophyll they cannot make their own food by photosynthesis. They must therefore absorb carbohydrates from the plant or animal matter on which they live. Having got s source of supply of carbohydrates they can themselves convert these substances into the more complicated ones needed to make cellulose for cell walls, and for proteins and protoplasm. The last two can only be formed if the fungus has a source of nitrogen and other more complex chemicals from an outside source, so for this reason a lot of fungi are rather specialized in their choice of where to grow. Like the animals, fungi are dependent upon green plants for their food and could not live without them. So it is that the first living matter to colonise a new piece of ground will be something which can manufacture its own food, without depending on any other life form and it must therefore be a green plant whether one celled or multi celled. When this is established, fungi and animals will appear either to grow on or eat the plant or live on the organic matter which occurs when it dies.