570 RESEARCHES ON FUNGI 



characteristic loose arrangement of the spore-bearing basidia in the 

 hymenium of Armillaria mellea, Marasmius oreades, Russula ochroleuca, 

 Amanita rubescens, Amanitopsis vayinata, Collyhia radicata, and Pluteus 

 cervinus. 



The development of the gills of Pluteus cervinus is discussed w'ith 

 special reference to the cystidia. The cystidia, which possess 3-6 

 terminal hooks or prongs, attain maturity before the spores begin to 

 develop. In a young fruit-body, just before the expansion of the pileus, 

 they cross the interlamellar spaces. The wall of that part of each 

 cystidium which projects across an interlamellar space is much thickened 

 and thus strengthened mechanically. The terminal hooks or prongs 

 are somewhat recurved, so that they do not penetrate the opposing 

 hymenium against which they may be pressed. The distribution and 

 minute structure of the cystidia suggest that the cystidia function as 

 interlamellar space-makers in the same manner as in certain Coprini. 



In the Armillaria Sub-type, relatively to the Panaeolus Sub-type, 

 there is on the whole a more rapid development of the individual 

 spores. The Armillaria Sub-type is regarded as more primitive than 

 the Panaeolus Sub-type. 



Chapter V. — The Inocybe Sub-type has been established to receive 

 species which have a hymenial organisation intermediate between that 

 of the Panaeolus Sub-type on the one hand and the Armillaria Sub-type 

 on the other. Species which appear to occupy this intermediate position 

 are : Inocybe asterospora, Galera tenera, Psathyra corrugis, and Russula 

 emetica. 



Chapter VI. — In the Inaequi-hymeniiferae or fungi of the Coprinus 

 Type : (1) the gills are very thin ; (2) the gills are not wedge-shaped 

 but, on the whole, parallel-sided or subparallel-sided ; (3) the gills are 

 not positively geotropic but ageotropic ; (4) usually, at maturity, the 

 hymenium on one side of a gill looks sHghtly downwards and that on 

 the other side slightly upwards ; (5) the spores ripen in succession from 

 below upwards on each gill ; (6) the spores are discharged in succession 

 from below upwards on each gill ; and (7) autodigestion proceeds from 

 below upwards on each gill and removes those parts of the gills which 

 have become spore-free and which, if they continued in existence, would 

 become mechanical hindrances to the fall of the remaining spores. In- 

 cluded within the Inaequi-hymeniiferae are all the species of the genus 

 Coprinus. 



Less fundamental characters of the Coprinus Type are : (1) the gills 

 blacken from below upwards ; (2) the number of generations of basidia 

 is in most species limited to two, but in a few species it is increased 

 to either three or four ; (3) the basidia in most species are dimorphic — 

 long and short, but in a few species they are either trimorphic or tetra- 

 morphic, i.e. of three or of four different lengths ; (4) the basidia are 

 laterally crowded together so that the spores of the longer basidia often 



