I9IS.] DEVELOPMENT OF AGARICUS RODMAN! 325 



with that of Agaricus campestris, arvensis, and a number of other 

 species, the veil is usually not ripped up from the lower part of the 

 stem as it is in the other species. A thin layer on the stem below 

 the annulus is often cracked into distinct areas or patches, the mar- 

 gins of the areas sometimes being partially exfoliated. The partial 

 exfoliation of the under part of the lower Hmb of the annulus fre- 

 quently occurs, and then the lower limb itself has a double edge as 

 described above, and as shown in several of the figures of Plate I. 

 In Agaricus campestris, arvensis, augiistiis, suhrufescens, placo- 

 myces, and others, the freeing of the lower part of the annulus 

 from the stem is very extensive, since as the stem elongates the 

 veil is ripped off for a considerable distance. In Agaricus rodmani, 

 as the pileus expands, the lower limb of the veil clings to the stem, 

 splitting off from the outer surface of the pileus margin as the latter 

 is withdrawn. The inner or upper limb of the veil remains at- 

 tached to the edge of the pileus margin for a longer time, but is 

 eventually separated. 



IV. Origin and Development of the Lamellae. 



Origin of the Gill Salients. — The development of the hymeno- 

 phore is progressive and centrifugal. As described in the previous 

 section, the primordial hymenophore zone originates in conjunction 

 with the primordium of the pileus margin and lies in the angle sep- 

 arating the stem and pileus areas. The organization of the level 

 palisade zone of the hymenophore from the primordial stage, begins 

 in the older region, i. e., next the stem. The margin of the pileus, 

 primordial hymenophore and palisade zone all progress by growth 

 in a centrifugal direction, the younger, later stages succeeding the 

 earlier. The lamellae succeed the level palisade zone and arise as 

 downward growing salients of the same. These salients begin 

 next the stem (or in some cases on it). They are regularly spaced 

 and progress in a radial, centrifugal direction. The origin of the 

 salients from the level palisade stage is well shown in Figs. 17-21. 



In Figs. 18 and 20, different stages in the origin of the salients 

 are shown. Three gill salients are seen in Fig. 20. At the left 

 side of Fig. 20 is the level palisade. Next it to the right is a very 

 low salient. Continuing to read toward the right, the second and 

 third salients are successively stronger. While the hyphal struc- 



