CHAPTER II.— DIFFERENTIATION OF THE THALLUS. — SCLEROTIA. 37 



The development of these sclerotia is slow ; it required for instance about four 

 weeks, according to Tulasne's observations, in the months of July and August in the 

 flowers of Brachypodium sylvaticum. In this case, when the sclerotia beo-an to 

 develope, drops of a saccharine fluid were observed to appear ; but it is uncertain 

 to what extent they were connected with the formation of the sclerotia or with that of 

 the gonidia. 



It sometimes, but rarely, happens that the Fungus is developed beneath the point 

 of attachment of the ovary ; when this happens the ovary preserves its proper form 

 and is carried up between the paleae on the apex of the sclerotium, and there withers 

 away before its time. 



The sclerotia when fully formed and matured pass into a resting stale, the 

 duration of which varies in species and in individuals with external and internal 

 causes, as is the case with seeds, tubers, and rhizomes. It depends on the habits 

 of life of the species in the natural condition whether the period of rest is 

 confined for example to winter, as is the case with Claviceps, Peziza Curreyana, 

 and P. Duriaei, or to summer, as in Typhula gyrans, T. variabilis, andT. phacorrhiza, 

 or is not constantly connected with the time of year. In the former case the time of 

 rest may only be slightly shortened in some species by changing the external 

 conditions, as the example of Claviceps especially shows. 



Sclerotia if kept dry will retain their power of development for a long time 

 unimpaired ; those of Peziza Sclerotiorum for more than a year, according to Brefeld 

 for several years, those of Claviceps for about a year ; after about that time those 

 of the latter species and of Peziza Fuckeliana also usually lose their vitality. 



The external conditions for the further development of the sclerotia are the 

 ordinary general conditions for germination, sufficient supply of water and oxygen 

 and a suitable temperature. The usual procedure under such conditions is as follows. 

 The sclerotium first absorbs water and swells, and then in a longer or shorter time, 

 often not till after some months, it sends out shoots at the cost of the food-material 

 stored up within it, and these develope directly into the sporophores characteristic of 

 the species. The sporophores in the species which form sclerotia, with the exception 

 which will be named further on, are compound structures. They accordingly 

 make their appearance as bundles of hyphae springing as branches from the elements 

 of the sclerotium, and in two ways according to the species. 



In one case (Figs. 18, 19) represented by Claviceps, Sclerotinia Fuckeliana and 

 S. Sclerotiorum, Typhula gyrans and T. phacorrhiza, the bundle of hyphae arises at 

 a certain spot in the medullary tissue and from branches of it which originate beneath 

 the rind ; the latter has no share in the new formations but is pierced through by the 

 advancing bundle of hyphae. A more minute description of the special circumstances 

 observed in Sclerotinia will be given in Division II. 



In the second case the bundle of hyphae is formed by the ramification of 

 outgrowths from the cells of the rind, as Brefeld rightly states in the case of Coprinus 

 stercorarius ; whether it is always a single cell that produces these shoots must for 

 the present remain undecided. Agaricus cirrhatus also shows this formation. 



Typhula variabilis is in some respects intermediate between the two cases ; here 

 according to Brefeld the initial bundle of hyphae appears on the surface of the rind, 

 neither springing apparently from a cell of the rind, nor causing an evident broad 



