44 



RESEARCHES ON FUNGI 



however, is uncertain and remains to be decided by future 

 observation. 



Description of the Fruit-body.— The very young pileus of 

 Psathyrella disseminata is ovate and pale buff. It is bounded above 

 by a firm pahsade layer made up of cells which are rounded when 

 seen from above (Fig. 26, B ; Fig. 27, A, a), and oval when seen in a 

 transverse section through the pileus-flesh (Fig. 27, B, a). Among 



the palisade cells are special cells which 

 are produced outwards into long slender 

 unicellular hairs or pilocystidia, each 

 having a swollen base and a simple 

 cylindrical shaft (Fig. 26, A and B ; 

 Fig. 27 : A, d; B, d and e). Each pileus, 

 as in Coprimis curtus or C. ephemerus, 

 bears several hundreds of these hairs. 

 In addition, on the top and sides of the 

 pileus above the palisade layer there lie 

 loose or easily detachable a number of 

 more or less spherical cells resembling 

 those of certain Coprini, e.g. C. stercorarius, 

 C. niveus, and C. curtus (Fig. 27, A, b ; 

 B, b). Many of these cells, as they grow 

 older, become brown and their walls 

 become decorated with small crystals of 

 calcium oxalate (Fig. 27, A, c ; B, c). The numerous hairs 

 and the loose spherical cells give the pileus a roughened 

 appearance. Hence, the pileus has been called scurfy by Massee ^ 

 and furfuraceous by Patouillard.^ When a young fruit-body, well 

 supplied with water below, is placed in air saturated with water- 

 vapour, the tops of the hairs rapidly excrete drops of a slimy fluid 

 (Fig. 27, d and e). Knoll, who regards the hairs as trichome- 

 hydathodes,^ has discovered that tlie drops, although soluble in 



Fig. 26. — Psathyrella dis- 

 seminata. A, vertical sec- 

 tion through a fruit-body. 

 The gills are not mottled 

 but evenly black. The 

 stipe is hollow, and the 

 pileus bears hairs on its 

 exterior. B, a surface view 

 of a part of a pileus 

 showing rounded cells and 

 one of the hairs. A, natural 

 size ; B, magnification, 

 220. 



^ G. Massee. British Fung us- Flora, London. 1892, vol. i, p. 345. 



- N. Patouillard, Tabulae anulyticae fungorum, Paris, 1883-1886, No. 351, 

 p. 160. 



^ r. Knoll, " Untersuchungen iiber den Bau und die Function der Cystiden und 

 verwandter Organe," Jahrb.fiir wiss. Bot., Bd. 50, 1912, pp. 457-468, 490. 



