1919] WALKER— PLUTEUS AA'D TUBARIA 9 



CHANGES TAKING PLACE IN TRAMA DURING DEVELOPMENT 



As can be seen in ligs. •36-38, 47, 48, and text ligs. 3 and 4, 

 the trama of the young gills is composed of slender, somewhat 

 parallel filaments which are scarcely 2 )u in diameter at first, but 

 soon become 2-2 . 5 m in diameter, as seen in fig. 38. The trama of 

 the gills is also very narrow and made up of relatively few filaments. 

 As expansion of the fruit body takes place rapid changes occur in 

 the trama. Fig. 25 is a transection of the gills of the plant shown 

 in median section in fig. 23, where expansion is just well begun. A 

 higher magnification of a part of these gills is shown in fig. 42. 

 Here one observes a great multiplication of the filaments making 

 up the trama, along with an enlargement of the individual cells. 

 The multiplication of cells takes place largely in the region just 

 below the hymenium, and is in the form of outgrowths of the sub- 

 hymenial cells. These outgrowths extend downward and toward 

 the center of the trama, as can be seen opposite A on the left of 

 fig. 42, and in text fig. 7, which 

 shows in a slightly diagrammatic 

 manner the detail of this part of 

 the section. 



These outgrowths continue 



their growth, maintaining a Fig. 7. -Portion of gill seen opposite 



downward and inward direction, A in fig. 42, showing beginnings of down- 

 as is seen in a slightly older fruit ^^'^■"^ outgrowths from subhymenium 



, , , - ^ V . , . , which develop during expansion of basid- 



body (figs. 26, 43), m which j^^^^p 

 many of these filarhents have 



reached the center of the trama. In these cells the protoplasm is 

 much more dense in the apical end, and in many cases largely con- 

 fined to this part. Figs. 27 and 44 show a still more extensive 

 development of these filaments which have now become 4-5 fx in 

 diameter, while figs. 28 and 45 show the gills when basidia have 

 reached a 4-nucleate stage, but before spore formation, with the 

 tramal cells about 7 jj. in diameter. At this stage these cells are 

 so long and thin-walled that some shrinkage takes place in all 

 fixed material. Figs. 46 and 49 show, just below the base of the 

 cystidium on the left, one of these filaments in good condition. 

 This can be seen more clearly in text fe. 6. Fig. 50 shows .the 



