I9IS-] DEVELOPMENT OF AGARICUS RODMANI. 311 



an excellent way the different details of the veil and annulus during 

 expansion of the plant. Those represented in Plate VIII., were col- 

 lected by Mr. Wood, June 28, 191 5, in the parking between the 

 sidewalk and street, on Stewart Avenue, in front of the Town and 

 Gown Club, Ithaca, N. Y. They were very robust specimens, and 

 show the great distance between the upper and lower, limb of the 

 annulus. They are reproduced here real size. 



A thin outer layer of the lower limb of the annulus is continuous 

 below with the outer layer of the stem, and also with a very thin 

 surface layer of the pileus. As the stem elongates at the time of 

 the expansion of the plant, this outer layer of the stem lags behind 

 and is thus torn into irregular patches shown very clearly in the two 

 upper left-hand figures of Plate VII. The edges of these patches are 

 frequently warped away from the stem, thus showing a tendency to 

 exfoliation. This is especially marked in the case of the surface 

 layer of the stem next the lower limb of the annulus. The warping 

 upward of this layer, after it has been severed from its connection 

 below, often gives the appearance of a double edge to the lower limb 

 of the annulus, as shown in the lower right-hand figure of Plate VII., 

 where the upper limb of the annulus has not yet broken away from 

 the pileus margin. 



The very thin layer on the pileus which is also continuous with 

 a thin outer layer of the lower limb of the annulus often shows a 

 tendency to exfoliation. This partial exfoliation of the stem and 

 pileus surface is clearly marked where the basidiocarps are some- 

 what soiled by contact with particles of earth, as they are likely to be 

 during the period of subterranean growth. 



The outer portion of the lower limb of the annulus, as Avell as 

 the corresponding thin, and partially exfoliating surface layer of the 

 pileus and stem are derived from the outer layer of the blematogen. 

 The blematogen layer, as I have interpreted it, is present in the genus 

 Agaricus as well as in Amanita. In the species of Amanita thus far 

 studied,^ the blematogen at length is clearly separated from the pileus 

 by a cleavage layer, arising from the gelatinization,, or other kind of 

 disintegration, of the external layer of the pileus primordium, thus 



3 Atkinson, Geo. P., "The Development of Amanitopsis vaginata," Ann. 

 Myc, 12, 369-392, pis. 17-19, 1914- 



PROC. AMER. PHIL. SOC, LIV. 219 U, PRINTED SEPT. 7, I915. 



