2l6 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



tissue undergoing considerable increase during development. 

 Some growth from the pileus margin is incorporated with it. 



Lepiota seminuda 



Material. — Lepiota seminuda is a very pretty, pure white, 

 rather small plant, 1-4 or 5 cm. high as it usually occurs in the 

 vicinity of Ithaca, N. Y. It grows in troops on decaying leaves 

 and small twigs or branches. It is covered with a loose powdery, 

 or mealy, substance of globose or broadly elliptical cells from the 

 blematogen. The partial veil is very frail, and usuall}' clings to 

 the margin of the expanded pileus, so that the mature plants are 

 usually exannulate. The slender stem is usually devoid of an 

 annulus, or has a delicate and fugacious one. Lacking a collar, 

 it is literally decollete, and may be said to be seminude. The 

 material for this study was collected during the summer of 1914, 

 in Cascadilla Woods on the campus of Cornell University, where 

 it has been found during a number of past years. The plants 

 were very numerous, thickly scattered over the leaves and decaying 

 twigs in a moist thicket, so that all stages from minute plants in 

 the earliest stages of the differentiation of pileus and stem funda- 

 ments to maturity were available. They were fixed in chrom- 

 acetic fluid, and the smaller specimens, as in the case of those of 

 Lepiota cristata, were lightly stained in toto with eosin, so that 

 their orientation in the paraffin could be readily seen. The 

 sections were stained with fuchsin. 



The pileus and stem primordia. — The youngest basidiocarp 

 studied was approximately 0.5 mm. long by 0.25 mm. in diameter. 

 A median longitudinal section is shown in figure 18. The young 

 pileus and stem i)rimordia are already organized within the ground 

 tissue and are enveloped by the blematogen of loose texture. 

 From the appearance of the sections of this young basidiocarp, I 

 am inclined to think that the young stem fundament is organized 

 first and that the pileus is organized later by progressive new 

 growth in the ground tissue from the stem apex, so that a sheaf- 

 like structure is formed surrounded by the blematogen: at least 

 the primordial areas of both stem and pileus are outlined prior to 

 the organization of the hymenophore fundament. 



Organization of the hymenophore primordium.—'YhQ hymeno- 

 phore primordium, as in Lepiota cristata, arises as an internal 



