127 
amounting to 80 or go °/o of the total ash, A recent analysis of 
Aspergillus spores, for instance, gave 45°96 “/o of potash and 39 64 
°/o phosphoric acid. This is noteworthy, because it is just these 
minerals which are apt to be rare in soils, or at least only accumu- 
lated with great difficulty by plants. | 
It soon became evident, however, that these destructive analyses 
of Fungi would never enable the physiologist to understand how the 
various chemical substances exist in the plant, and that we might as 
well expect to understand the construction and working of a watch by 
smashing it up in a mortar and dissolving it in acids, as hope to appre- 
hend the structure and functions of the fungus by these drastic 
measures; and although numberless delicate investigations continued 
to show that very curious and interesting chemical compounds can be 
obtained from Fungi—e.g., the poisonous alcaloids, Muscarin from 
Amanita muscaria, Ergotin from Claviceps purpurea, and the long 
series of brilliant colouring matters and organic acids, and of carbo-hy- 
drates, resins, etc. from Lichens and various Fungi—little progress 
was being made towards a solution of the principal problems. 
It was clear that every fungus contains the elements mentioned ; 
but it was by no means proved that all are necessary. Obviously the 
only way to decide the matter was to cultivate the fungus and offer 
it these elements in various proportions, and see whether and how it 
can build up its substance in each case. 
Now there are hundreds of ways of. presenting such elements to a 
growing fungus. It is very easy to make up doses of substances such 
as calcium carbonate, potassium sulphide, magnesium phosphate, 
sodium nitrate, etc., in water, but although such a mixture would 
contain all the elements required, it was soon found that no fungus 
would grow in it, and that the form in which the elements are com- 
bined is an essential point in the food of Fungi. Many trials led to 
the conclusion that the carbon especially must be presented in particu- 
lar forms, as otherwise the fungus cannot avail itself of the supply, 
and this was soon explained when the consequences of the lack of 
chlorophyll were understood. But it was also found that the nitrogen 
constituents must also be presented in special forms, or the fungus 
could not flourish: for instance it is as a rule useless to offer nitrates. 
And as experience accumulated similar facts came out in other 
connections. 
~ An excellent food-mixture for many Fungi was then shown to be 
such as the following. 
Ordinary cane-sugar, as the principal source of the carbon ; 
ammonium tartrate, supplying nitrogen, and the ashes of yeast, con- 
taining the necessary mineral elements; the oxygen and hydrogen 
needed being also afforded by the organic materials and water. Many 
other similar mixtures were also used successfully. But several 
curious and instructive discoveries soon resulted from culture 
experiments in such media. = 
It was found that the cane-sugar is first altered by the fungus and 
broken up into two other sugars—fructose (levulose) and glucose 
