100 SAPROPHYTES AND THEIR RELATION TO DECAYING BODIES. 
that their colour is quite altered. The so-called “mushroom-spawn”, used in the 
cultivation of mushrooms, is also nothing but a mycelium, which entirely invests 
the manure employed in the cultivation of that fungus, and gives it a white 
mottled appearance. 
In addition to Fungi, however, a number of Mosses, Liverworts, Ferns, Lycopods, 
and Phanerogams take up organic compounds from the products of decay to serve 
as their food. 
In deciding whether a plant takes up only the mineral substances rendered 
soluble by the decomposition of the soil, or only organie substances disengaged 
by the decay of dead plants and animals, we depend generally on the condition 
and appearance of the nutrient substratum, and, in particular, on its composition, 
i.e. Whether it is exclusively or predominantly organic. But such observations 
give a very uncertain indication. For, on the one hand, it is possible for plants 
rooted in a substratum of decaying matter to take nothing but mineral salts (%.e. 
inorganic compounds) from it; and, on the other hand, it frequently happens that 
sand or clay, apparently uncontaminated with organic matter, is saturated by 
water which oozes from a layer of humus in the vicinity, and brings with it 
organic compounds in solution. The following facts are instructive with reference 
to the former of these two phenomena. Maize, barley, and other cereals may be 
reared in fluids, so prepared as to contain a small quantity of mineral food-salts 
dissolved in distilled water (12 mg. potassium phosphate, 12 mg. sodium phosphate, 
27 mg. calcium chloride, 40 mg. potassium chloride, 20 mg. magnesium sulphate, 
10 mg. ammonium sulphate, and a few drops of iron chloride in a litre of distilled 
water), all organic compounds being carefully excluded. When the plants germinate, 
they develop roots which descend in the liquid and absorb from it mineral salts 
according to their requirements. They produce stems, leaves, flowers, and, ulti- 
mately, seeds capable of germination. Other plants of maize or barley reared 
simultaneously in richly-manured ground develop likewise leaves, flowers, and fruit. 
Moreover, analysis of the ash in both cases reveals the fact that the plants which 
took their nutriment from the manure contain the same salts as those reared in the 
made-up solution of salts free from organic compounds. Hence, the conclusion may 
be drawn that a plant of this kind is capable of obtaining an adequate supply of 
food-salts equally well, either from earth free from humus and manure, or from 
humus or manure themselves. The experiment further shows that, in the latter 
case, organic compounds need not necessarily be absorbed, in addition to the mineral 
constituents of humus or manure which are disengaged during decomposition. 
We must next refer to a fact in connection with the second point above men- 
tioned, viz. that plants rooted in sand or loam devoid of humus may yet have 
organic compounds brought to them by water filtering through a stratum of humus 
near at hand. The fact in question is, that the very water which one would least 
expect should contain organie compounds, that, for instance, of cold mountain 
streams, does very generally include traces of such compounds. On looking through 
analyses of mineral springs, one finds for the most part, amongst their constituents, 
