CYSTIDIA 17 



continued absorption of water, still be able to stretch its stipe and 

 expand its pileus. The diminution in the supply of food materials 

 might lead to the non-development of the basidia. I have attempted 

 to induce sterility in Coj^rinus 'plicatiloides by mechanically dis- 

 turbing the substratum of young fruit-bodies, and have partially 

 succeeded. In one experiment a large fruit-body became pale 

 yellowish-grey at maturity, and it was found that the number of 

 basidia which had developed in the neighbourhood of the stipe was 

 very much below the normal. However, it must not be supposed 

 that sterile fruit-bodies are produced only after artificial disturbance 

 of the substratum, for in one instance, in a culture left undisturbed 

 for some weeks, two fruit-bodies of equal size came up side by side 

 with the bases of the stipes in contact, yet one of them was perfectly 

 fertile and the other quite sterile. 



Cystidia. — The significance of cystidia, once thought by Corda, 

 Hoffman,^ Worthington Smith,- and others, to be male organs, still 

 seems not to have been elucidated with any certainty. According 

 to Cooke,^ " The usual interpretation of the function of cystidia is, 

 that they are simply mechanical contrivances projecting from the 

 hymenium and thus keeping the gills or lamella3 apart." Possibly 

 this view may be correct for certain species of Coprinus, erj. 

 C. micaceus, where large cystidia are found on the gill surfaces ; but 

 where cystidia coat the swollen gill edges, as in C. comatus, we 

 may regard them as packing cells. They form cushions where 

 the gills are in contact with each other and the stipe, and they 

 probably facilitate the separation of these structures on the ex- 

 pansion of the pileus. Stress has already been laid on the necessity 

 for the provision of spaces between adjacent gills during develop- 

 ment, owing to the adhesiveness of the spores ; but these spaces 

 can be brought into existence, e.g. in C. comatus, by other 

 means than by the production of cystidia {vide infra. Chap. XIX. ; 

 Plate I. Fig. 5 ; Plate III. Fig. 14). In the genus Peniophora, the 



^ H. Hoffman, "Die Pollinarien unci Spermatien von Agaricus," Bot. Zeit., 

 xiv., 1856, pp. 1.37-48, 153-6.3. 



2 Worthington Smith, " Keproduction in Coprinus radiatus," Grevillea, vol. iv., 

 1875-6, pp. 53-65. 



' M. C. Cooke, Introduction to the Study of Fungi, London, 1895, p. 41. 



B 



