I9I5.] DEVELOPMENT OF AGARICUS RODMANI. 327 



gill salients thus crowd against the intervening neutral palisade cells, 

 more strongly against their free ends. This presses these intervening, 

 neutral, radiating areas of the original level palisade into the form of 

 ridges which thus alternate with the radiating gill salients. These in- 

 tervening ridges between the young gill salients are very conspicuous 

 in a corresponding stage of gill development in Coprimis micaceus as 

 I have shown in another paper. This situation is a comparatively 

 old stage in the development of the lamellae and is one of the peculiar 

 features presented by a number of the Agaricacese, which led Levine^^ 

 to mistake these intervening ridges between comparatively old gill 

 salients for the first ridges to appear in the hymenophore primordium 

 of Coprinus micaceus. These ridges he thought were the first evi- 

 dence of the gills. The gills were described as arising from the split- 

 ting of these first ridges and the union of approximate halves of ad- 

 jacent ridges to form the gills between them. This matter will be 

 referred to below when another peculiar situation is described which 

 also assisted in leading this author astray. 



Relation of the Different Phases of Hymenophore Development 

 in the Young Basidiocarp. — Figs. 17-23 represent different phases 

 of the organization and development of the hymenophore in a single 

 basidiocarp, during an intermediate stage of its development. The 

 relation of these different phases is determined by a study of longi- 

 tudinal serial sections passing from near the stem to the margin of 

 the pileus. With the exception of Fig. 20, Figs. 17-23 are all from 

 the same plant, selected to represent the relation of different phases 

 of the young hymenophore. The sections from which the photo- 

 graphs were taken were parallel with the axis of the stem, and thus 

 were nearly or quite perpendicular to the hymenophore, or under 

 surface of the pileus. The general plane of the hymenophore, or 

 under surface of the pileus, is slightly arched, but for all practical 

 purposes of this study, the plane is perpendicular to the stem axis, 

 so that the sections are perpendicular to the general hymenophore 

 surface, or plane. Fig. 17 is from a section near the stem, cor- 

 responding to line 4 in diagram 6 (diagram 6 is intended to illustrate 

 the situation presented by the figures in Plate 5, but serves to illus- 



31 Levine, M., " The Origin and Development of the Lamellae in Cop- 

 rinus micaceus," Am. Jour. Bot., i, 343-356, pis. 39, 40, 1914. 



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



