1919] WALKER— PLUTEUS AND TUBARIA 5 



it, SO that in the tangential longitudinal section shown in fig. 10, 

 and more highly magnified in fig. 35, the gills appear to extend as 

 strands from pileus to stipe. The direction of the growth of the 

 hymenophore, however, as shown in text fig. iB, continues to be the 

 same as in the level palisade condition (figs. 30, 32), so that the cells 

 making up the fundament of the trama (fig. 35) are transverse sec- 

 tions of filaments extending outward at right angles to the plane of 

 the sections. The hyphae making up the subhymenium and the fun- 

 dament of the trama are smaller than in theyoungpalisadecondition. 



Figs. 12-14 show a slightly older but somewhat depauperate 

 basidiocarp in median and tangential longitudinal section. Here 

 the young gill salients whose development is centrifugal are clearly 

 shown. Figs. 33 and 34 show the detail of this specimen. The 

 depauperate condition of the fruit is shown by the scanty proto- 

 plasmic content and by the enlargement of the cells to a condi- 

 tion characteristic of older fruits. The development having been 

 stopped at this age, the relation of the parts would probably remain 

 identical with those of the normally developing basidiocarps. That 

 this would be the case is substantiated by the observation of other 

 depauperate fruits sectioned, in which development had been 

 arrested at all stages. 



Because of the strong incurving of the margin of the pileus after 

 the beginning of gill development, and as the expansion of the fruit 

 body progresses along with gill development, the palisade layer 

 constantly present toward the margin of the pileus is always on the 

 interior (morphological under-side) of the pileus margin as seen in 

 tangential section (figs. 15-18). In fig. 18, and better in a higher 

 magnification (fig. 36), the palisade layer is thus shown. In figs. 

 19-22 a slightly older fruit body is shown, in which the hymeno- 

 phore shows gills in the young salient stage on the incurved por- 

 tion of the pileus. Fig. 37 is a higher magnification of the section 

 shown in fig. 22. In this fruit body the gills are so broad that the 

 tangential sections show the gills attached above and below, 

 but in each case attached to the morphological under-side of the 

 pileus, their point of origin. Text fig. 2 shows how the sections in 

 this series were cut, and that the attachment of these gills above 

 and below is due to the incurved form of the pileus. 



