CHAPTER IT. DIFFERENTIATION OF THE THALLUS. SCLEROTIA. 33 



and some are prolonged into short irregular hairs or papillae, while in others the 

 membrane is irregularly torn on the outer side of the cell and the exterior surface 

 is thus rendered rough and uneven. 



f. The sclerotia of some Typhulae, T. phacorrhiza, T. gyrans, T. Euphorbiae, Fuckel, 

 T. graminum, Karst., &c. have the gelatinous medulla with cartilaginous consistence 

 of the type a, with slight differences as regards the thickness and firmness of their 

 membranes in the several species. The hyphae contain a clear watery fluid which 

 sometimes has granules sparingly distributed through it ; in T. graminum only they 

 are densely filled with homogeneous turbid protoplasm. The rind in these species is a 

 single layer of cells of uniform height connected by their sides without interstices, 

 which are evidently the peripheral segments of the medullary hyphae, unlike them 

 as they may be in structure. The cells are tabular or shortly prismatic in shape, 

 their lateral walls often curved and sinuous ; the inner and lateral walls are slightly, 

 the outer walls very strongly thickened in the manner of the outer wall of the 

 epidermal cells in vascular plants, and have their outer surface smooth (Fig. 15 c) or 

 warted (Fig. 15 , b). The rind is thus remarkably like the firm epidermis without 

 stomata of many vascular plants. 



g. In the sclerotia of Typhula variabilis, Riess, and Peziza Curreyana the 

 structure of the rind is essentially the same as in the last type, but the white or in 

 P. curreyana the rose-red medullary tissue is a weft of cylindrical hyphae with 



FIG. 15. a and b sclerotium of Typhula phaeorrhiza. a piece of a thin transverse section ; r r rind-cells, q q outer layers 

 of the same, b piece of the rind flattened out, seen from the outside ; at s the outside of outer layers only is seen without the 

 lateral walls of the cells, c cortical layer of the sclerotium of Typhula gyrans flattened out and seen from the outside^ Magn. 

 390 times. 



air-spaces. The hyphae are thin-walled in Typhula with dense, granular contents ; 

 in P. curreyana the membrane is thickened and stratified, and the medullary tissue 

 is more compact towards the periphery as is the case in type a. 



h. The sclerotia of species of Claviceps, the blunt trilateral horn-shaped bodies 

 which develope in the flowers of the Gramineae and Cyperaceae at the expense of 

 the ovary and are known by the name of ergot, consist in the mature state chiefly 

 of a dirty-white medullary tissue surrounded by a violet-brown rind. The medulla 

 has the character of a pseudo-parenchyma formed of cylindric prismatic cells, which 

 are on an average from one to four times as long as broad. The cells are arranged 

 in straight or sinuous longitudinal rows, and the history of their development shows 

 that they possess the characters of the fungal hyphae. This may also be clearly 

 seen even in ripe sclerotia, in the interior of which clefts and fissures are often 

 found clothed or loosely filled with a thin felt ; sections show that the felt is composed 

 of interwoven hyphae, which spring as branches from the rows of cells of the 

 compact tissue and have the same characteristics, except that their weft is looser. 

 The medulla has usually shorter and broader cells towards the periphery of the 

 sclerotium than in its centre. The cells are everywhere provided with tolerably 

 thick colourless membranes, and are usually firmly grown together on every side 

 without interspaces. They contain large colourless drops of oil. 

 [4] 



