30 RESEARCHES ON FUNGI 



itself, is not necessarily a proof of close relationship. For the 

 purpose of building up a genealogical tree of the Hymenomycetes 

 it is necessary to proceed along the old and safe lines, i.e. one must 

 take into account all the characters which the species exhibit and 

 not merely a few of them. Notwithstanding these remarks, we are 

 fully justified in classing Psathyrella disseminata and Lepiota cepae- 

 stipes together from the physiological stand-point of the production 

 and liberation of spores, for they carry out this one main function 

 of their fruit-bodies in essentially the same manner. A parallel to 

 the physiological mode of classification here adopted is to be found 

 among the Phanerogamia in the division of the species into anemo- 

 philous, hydrophilous, and entomophilous groups, according to 

 whether the wind, water, or insects are employed as agents in the 

 cross-pollination of the flowers. 



Psathyrella disseminata. Its Relation with Tree Stumps. — 

 Psathyrella disseminata is one of the best-known of the Melanosporae, 

 for it is frequently seen in late summer and autumn coming up in 

 its favourite habitat upon and around old stumps of trees. The 

 individual fruit-body is inconspicuous ; for it has but a dingy grey- 

 appearance and is of small size, its stipe being rarely more than one 

 and a half inches high, and its expanded pileus being, as a rule, only 

 from one-third to one-half an inch in width. But the fruit-bodies 

 are gregarious, and they make up for their sombre hue and small 

 dimensions by their often mxultitudinous number. Sometimes, after 

 rain, many hundreds of them — or even thousands — spring up over- 

 night in one place, so that the phenomenon of their occurrence excites 

 the astonishment of even the dullest observers. 



A group of fruit-bodies coming up upon the soil around an 

 inverted tree-stump is shown on a reduced scale in Fig. 18, and a 

 small portion of the same group with the fruit-bodies of natural 

 size and in their natural position is shown in Fig. 19. The stump 

 had formed part of a healthy tree which was cut down about 

 eighteen months before the photograph was taken. As soon as the 

 tree had been felled, the stump was dug up, inverted, and set on 

 bare soil under some trees, so that it might support ivy and become 

 of ornamental value. Its destruction was soon begun by sapro- 

 phytes of which one of the most successful was Psathyrella dis- 



