CHAPTER II.— DIFFERENTIATION OF THE THALLUS. — SCLEROTIA. 30 



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 with a 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 Copfinus 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 



