﻿igi6] ATKINSON— COPRINUS 103 



thus effected. Because of the changing tensions to which the 

 plant is subject more or less during growth, the lamellae may likely 

 come in contact with the stem, the edges become more or less 

 flattened out, then become free, and then again come in contact 

 with the stem surface, and finally make the connection permanent, 

 until expansion of the plant begins at maturity. In fig. 24 the 

 lamella at the right, which had crowded slightly into the surface 

 of the stem, and whose marginal cells are only slightly spread, has 

 been slightly withdrawn from the stem during the smoothing out of 

 the paraffin ribbon. 



As the lamellae become more firmly crowded against the stem, 

 the portion in direct contact loses the deep staining quality which 

 the marginal palisade cells in common with the palisade cells of the 

 hymenium on the sides possess. This is due to the fact that the 

 greater part of the marginal palisade cells are squeezed out laterally, 

 while the few which remain take on a more vegetative function, 

 and, with the new growth of the trama hyphae here, form the 

 interlacing and rather loose connection with the stem. 



There is another interesting feature in the origin and develop- 

 ment of the lamellae which requires a clear exposition, because it is 

 present not only in the three species of Coprinus treated here, but 

 also in the vast majority of the agarics, and perhaps with very few 

 exceptions in all. Unless clearly analyzed, the situation might be 

 misleading and result in an incorrect interpretation of the origin of 

 the gills. The situation is presented in fig. 20, where the gills 

 both to the left and right show the trama distinctly continuous 

 with the tissue above and below. This situation may, and does 

 often, occur even in quite young phases of the origin of the lamellae. 

 This figure is of a tangential section parallel with the axis of the 

 stem but near the margin of the pileus. Epinastic growth of the 

 pileus margin causes it to curve in more toward the stem. Since the 

 lamellae originate as radial salients on the inner side of the pileus and 

 grow in breadth perpendicular to the surface of their origin, sec- 

 tions parallel with the axis of the stem but through the margin of 

 the pileus would be parallel to a tangent of the pileus curve in this 

 region. When the sections are made with the knife traveling from 

 the stem through the far side of the basidiocarp, at the extreme left 



