The science of life : fully illustrated in tone and line and including many diagrams

THE LOWLY AND MINUTE

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Fig. 118. The graceful spore-cases of six species of slime-mould—magnified to about twenty times life size. They are common on rotting wood, dead leaves, and so on.

and it can flow around and thus consume the matters upon which it lives. It will turn aside from its course to flow over an attractive lump of food. In most cases only dead and decaying things are taken into this shapeless interior to be digested, but there are species which feed on living vegetable prey—on fungi, for example.

A botanist once made a slime-fungus flow through a dense pad of wet cotton wool. As it progressed, its substance broke up into a multitude of parallel streamlets to pass through the interstices of the wool, and as it emerged on the other side they joined up again. Previously it had contained great numbers of the dark brown spores of the fungus on which it was feeding, but now it was colourless; they had all been filtered out and left behind as the protoplasm oozed through the wool. Many slime fungi spend most of their lives thus permeating through rotten wood.

Sometimes, under adverse conditions (such as drought) the creature passes into a resting condition. Part of its substance hardens to a horny consistency in order to protect the rest and forms a number of hollow capsules, each capsule housing a mass of fluid protoplasm with ten or twenty nuclei in it. This mass of capsules can live, motionless, without

giving a sign of life, for as long as three years. When conditions become more favourable—when the resting mass is moistened, for example—the hard cyst-walls are absorbed and the contents flow together into a single sheet again, and continue their slow, creeping life as if their long inanition had been only the sleep of a night.

So far our slime-mould has behaved more like an animal thana plant. It creeps about like an extremely sluggish animal ; not being green, it feeds like an animal. But its reproductive processes are definitely plantlike. Because of this alternation between an animal mode of life and a vegetable mode of reproduction the group is one of those frontier forms that have found a place both in zoological and botanical text-books. The slime-mould reproduces itself by means of spores, contained in fructifications that remind one of those of the true fungi. These sporangia, as they are called, are of various shapes, depending on the species to which they belong. Fig. 118 gives an idea of the range of form that is found. They may be spherical or oval or cylindrical ; they may rise on short stalks as knobs or cups or mushroom-like umbrellas. Usually they are extremely small and have to be examined with a low-power lens. Besides

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