CHAPTER II.—DIFFERENTIATION OF THE THALLUS.—SCLEROTIA. 39 
same in fragments of a sclerotium as in their corresponding sclerotia. It is natural to 
assume, without closer inquiry into the metabolism, that the cause of these phenomena 
lies in the difference in quantity of the reserve-material at the disposition’ of the plant 
according to the size of the sclerotia or their fragments, and that the not infrequent 
irregularities and apparent exceptions to the rule are due, other things being equal, to 
differences in quantity or quality in the reserve-material, which may occur also, be it 
remembered, where the size of the sclerotia or of its fragments is the same. 
The formation of the primordia and the further development of the sporophores is 
accompanied by the solution, transformation, and consumption of the food-material 
stored up in the sclerotia. The process begins at the point of origin of a primordium and 
spreads by degrees through the medullary tissue. In Claviceps, according to Tulasne, 
the oil disappears and its place is taken by watery fluid, the cell-membranes become 
thinner and ultimately very delicate, and the cells separate readily from one another. 
In the sclerotia of Sclerotinia Fuckeliana, S. Sclerotiorum, S.tuberosa, Typhula gyrans, 
&c. which are gelatinous witha cartilaginous consistence, the gelatinous thickening-layers 
of the hyphae become softer and pale and by degrees scarcely recognisable, so that the 
innermost layer only of the membrane can still be clearly seen as a delicate pellicle. 
The former firm union of the hyphae naturally comes to an end at the same time ; 
and a mass of granular matter which turns yellow with iodine collects in the cavities 
of the cells, and diminishes again in quantity as the sporophores increase in number 
and size. In Coprinus stercorarius, according to Brefeld, the granular protoplasm of 
the cells is replaced by a watery fluid, and the membranes become pale and 
undistinguishable. Ultimately in all these cases the medullary tissue almost entirely 
disappears. The rind at first takes no perceptible part in these changes; it remains 
behind after the disappearance of the medulla as a soft sac which collapses and decays. 
These processes take a longer or a shorter time in different cases. In Brefeld’s 
culture of Coprinus stercorarius they were over in 7-10 days. In most species they 
take much longer time. Sclerotinia Sclerotiorum, for instance, may put out new 
sporophores one after another during some months from one sclerotium, and develope 
them slowly before the supply of food is exhausted. I have found sclerotia of 
Agaricus cirrhatus (see on page 37), which had developed one or more sporophores 
and fully matured them, not sensibly different in consistence and structure from others 
which had not yet produced any; they might therefore repeat the production of 
successive sporophores and perhaps during a considerable time ; but this point 
remains to be determined. 
Some sclerotia, as those of the Sclerotinieae, of Coprinus stercorarius and 
Claviceps, are able in the mature state and as long as they retain their vitality to form 
new rind over wounds, such as cut surfaces which reach to the medullary tissue, 
provided they are exposed to the air but are protected from desiccation. The new 
rind resembles the old ordinary tissue in all essential points. It is formed by the 
medullary hyphae exposed by the wound sending out branches, which become woven 
together into a delicate felt and cover the surface of the wound. The inner layers of 
this covering which are next the uninjured medullary tissue then develope into a new 
rind, while the outer ones dry up and disappear. If such wounded places are kept 
in a nutrient solution, the branches put out by the medullary hyphae on the exposed 
points may, in the Sclerotinieae at least, develope into vegetating mycelial hyphae 
