52 RESEARCHES ON FUNGI 



rapid producers of individual spores, and of such genera as Panaeolus, 

 Stropharia, and Coprinus as slow producers of individual spores. 



Fayod, who was an excellent observer, asserts in his Prodrome 

 that the Leucosporae, with few exceptions, have simple spore- 

 walls ; whilst, in the majority of the Agaricineae with pigmented 

 spores, the spore- walls are double. He further asserts that, where 

 a spore is coloured and two-coated, it is the endospore and not 

 the exospore which contains the pigment. 1 I have not as yet 

 sought to verify these statements in a detailed investigation ; but 

 it may be remarked that I have only been able to observe a single 

 wall-layer in the spores of species of Marasmius, Collybia, and Armil- 

 laria, whereas in the large spores of Coprinus sterquilinus when 

 mounted in water I have clearly perceived, on the side of the spore 

 opposite to the hilum, an outer white membrane surrounding an inner 

 membrane containing the dark pigment. Moreover, I have confirmed 

 Hansen's 2 statement that, when the spores of Coprinus stercorarius 

 are treated with chlor-zinc iodine, an outer colourless cell-wall or 

 exospore swells up and removes itself from an inner pigmented 

 cell-wall or endospore. 3 If we assume Fayod's statements to be 

 correct, we may consider that, in general, pigmented spores take 

 longer to develop than colourless ones, not merely because they have 

 to manufacture a pigment but because they have to form an inner 

 wall which comes to contain that pigment. 



Another factor which is probably correlated with the slower 

 development of highly pigmented spores is that, where these spores 

 are concerned, as compared with colourless spores, there is a relatively 

 greater crowding of basidia producing spores simultaneously on a 

 unit area of the hymenium. The contrast in this respect between, 



1 M. V. Fayod, " Prodrome d'une Histoire Naturelle des Agaricines," Ann. set. 

 nat., T. IX, 1889, pp. 269, 302, and 330. 



2 E. C. Hansen, " Biologische Untersuchungen iiber Mist-bewohnende Pilze," 

 Bot. Zeit., 1897, p. 114. 



3 In some Ascomycetes having pigmented spores, the spore-wall consists of 

 two layers as in Coprinus stercorarius. Thus a double spore-wall is present in 

 Daldinia vernicosa and D. concentrica ; for A. S. Rhoads (" Daldinia concentrica 

 a pyroxylophilous Fungus," Mycologia, vol. x, 1918, p. 283) has pointed out that, 

 when the spores of these species are mounted in dilute alkaline solutions, the colour- 

 less exospore dehisces along a single equatorial line and thus separates in two pieces 

 from the black endospore. 



