MICHIGAN ACADEMY OB' 1 SCIENCE. 
43 
of preservative against decay, more especially in such fruits as those 
upon which perithecia do not grow. 
That a mycelium shpuld stimulate the formation of starch within 
cells of such tissue as an apple which has long since been detached from 
the tree, is surprising because the cells are no longer living in the sense 
that cell division could be further carried on; and indeed the nuclei 
seem to be, in many cases, entirely disorganized. But it has long been 
regarded that the nucleus is the functional organ of the cell, without 
which none of the usual operations of the cell can be carried on. The 
thickening of the cell walls and the formation of starch grains seem to 
be produced independently of the nucleus of the apple cell, and it would 
therefore appear as though the stimuli produced by the presence of 
the hyphae of the fungus effect the same results in this respect as that 
which might have been produced by a nucleus. But the nuclei which 
might happen to remain alive and intact in the fleshy part of a ripe 
apple, do not seem to be capable of developing thick walls, or of per¬ 
forming the function of building up starch grains after the fruit comes 
to maturity. The carbohydrates are present in the cells, and these car¬ 
bohydrates are so modified by the stimulus of the fungus, that part 
becomes starch and part cellulose. There is, however, a suggestion 
that starch grains are formed first, and then, later, dissolved and built 
up into cellulose. It was not possible to see this process being carried 
on, and the suggestion arises only out of the fact that when the walls 
are thickest the number of starch grains is smallest. 
The conclusion is naturally reached, therefore, that a fungus may 
actually stimulate the direct operation of Maiding up —as the process 
of cellulose formation has frequently been called,—as well as the almost 
universal one of breaking down. That it can do this in a body outside 
itself, and th!e body not in a growing condition, is a fact at once curious 
to a high degree. The formation, then, of cellulose and of starch, in 
the laboratory, may not be quite so stupendous a process after all. 
Among parasitic fungi it commonly happens that starch grains are 
present in the neighborhood of the fungus mycelium, but this has been 
ascribed to the fact that the host plant—as a living, growing plant— 
responds in this way to the stimulus produced by the parasite. Galls 
are developed on plants as a result of all the stimuli induced by the 
sting of an insect. But an insect could not produce a gall in a leaf 
severed from the plant. So that when the fungus causes a development 
of cellulose or of starch grains in the cells of an apple in winter time, 
or any time after the apple is detached from the tree, it is performing 
an operation which seems to be different from that of the parasite 
growing upon the living plant. From this arises the question as to 
when a plant, or part of a plant, is really dead ; and this is probably 
one of the most interesting as well as the most subtle questions in the 
field of physiology today. It is thought that the peculiar phenomena 
resulting from the operation of the black rot fungus upon the apple 
throws some faint rays of light upon the question. The flesh of the 
apple can scarcely be considered dead, even though the nuclei may have 
become disorganized, because the other cell content is capable of re¬ 
sponse to stimuli, and can act apparently of its own motive force. 
It should also be said that several fungi are capable of causing the 
