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BOTANICAL GAZETTE 



of the young basidiocarp, due to the more rapid growth of the pileus 

 and stem primordium, and the less rapid growth of the fundamental 

 plectenchyma below the pileus primordium, in the angle between 

 it and the stem. The fundamental plectenchyma is thus torn 

 apart, and in those cases where this annular cavity is well formed 

 prior to the origin of the palisade layer of the young hymenophore, 

 the surface of the cavity is very ragged from the loose hyphae pro- 

 jecting to different distances in the cavity. This ragged appear- 

 ance disappears over the roof of the cavity as the palisade layer 

 is established. 



The cavity and the palisade layer 2 first appear near the stem 

 fundament. The pileus primordium is at this time comparatively 

 limited in extent. The margin is younger than the portion next 

 to the stem. As growth continues, there is centrifugal growth 

 of the pileus at the margin, and this is accompanied by the centrifu- 

 gal extension of the annular cavity, followed by the centrifugal 

 extension of the palisade layer. In this way the elements are 

 younger toward the margin of the pileus and older toward the 



In the forms described, belonging to this type, the lamellae origi- 

 nate in the form of downward projecting ridges or folds of the pali- 

 sade layer. These ridges or folds begin at or near the stem, the 

 newer, younger, radial extensions of them proceeding centrifugally; 

 while the lamella increases in width downward by increase of the ele- 

 ments of its surface, and growth of the trama hyphae extending from 

 the pileus above. The first evidence of a downward projecting ridge, 

 or fold, which is the fundament, or early stage of the lamella, is the 

 result of the increase in size and number of the elements of the pali- 

 sade layer of the young hymenophore in a line radiating from or near 

 the stem outward, or by the more rapid elongation of the trama 

 hyphae of the young pileus along this line and next to the palisade 

 layer, or by both processes combined. These elongating trama 

 hyphae, as they pass into the gill salient, form the beginning of 

 the trama of the lamella. 



