FUNGI. 83 



several centimetres within a few hours. At the same time 

 that the stalk is elongating, the cap spreads out, radial clefts 

 appearing on its upper surface, which flatten out very much as 

 the folds of an umbrella are stretched as it opens, and the 

 spaces between the clefts appear as ridges, comparable to the 

 ribs of the umbrella (Fig. 48, B). The under side of the cap 

 has a number of ridges running from the centre to the margin, 

 and of a black color, due to the innumerable spores covering 

 their surface (C). Almost as soon as the umbrella opens, the 

 spores are shed, and the whole structure shrivels up and dis- 

 solves, leaving almost no trace behind. 



If we examine microscopically the youngest specimens procurable, free- 

 ing from air with alcohol, and mounting in water or dilute glycerine, we 

 find it to be a little, nearly globular mass of colorless filaments, with 

 numerous cross-walls, the whole arising from similar looser filaments 

 imbedded in the substratum (Fig. 48, G). If the specimen is not too young, 

 a denser central portion can be made out, and in still older ones (Fig. 48, 

 H) this central mass has assumed the form of a short, thick stalk, crowned 

 by a flat cap, the whole invested by a loose mass of filaments that merge 

 more or less gradually into the central portion. By the time the spore 

 fruit (for this structure corresponds to the spore fruit of the Ascomycetes) 

 reaches a height of two or three millimetres, and is plainly visible to the 

 naked eye, the cap grows downward at the margins, so as to almost en- 

 tirely conceal the stalk. A longitudinal section of such a stage shows the 

 stalk to be composed of a small-celled, close tissue becoming looser in 

 the cap, on whose inner surface the spore-bearing ridges ("gills" or 

 Lamellw) have begun to develop. Some of these run completely to the 

 edge of the cap, others only part way. To study their structure, make 

 cross-sections of the cap of a nearly full-grown, but unopened, specimen, 

 and this will give numerous sections of the young gills. We find them to 

 be flat plates, composed within of loosely interwoven filaments, whose 

 ends stand out at right angles to the surface of the gills, forming a layer 

 of closely-set upright cells (basidia) (Fig. 48, D). These are at first all 

 alike, but later some of them become club-shaped, and develop at the end 

 several (usually four) little points, at the end of which spores are formed 

 in exactly the same way as we saw in the germinating teleuto spores of 

 the cedar rust, all the protoplasm of the basidium passing into the grow- 

 ing spores (Fig. 48, E, F). The ripe spores (E, sp.) are oval, and possess 

 a firm, dark outer wall. Occasionally some of the basidia develop into 



