iqiq] walker— PLUTEUS AND TUBARIA II 



loosely interwoven hyphae about 2-3 ju in diameter, the external 

 ones having firmer walls and taking the stain slightly more than 

 those toward the interior. The fruit body illustrated in fig. 53 is 

 smaller but shows some differentiation. There is a superficial 

 zone made up of very loosely interwoven hyphae with firm walls. 

 This region marks the beginning of a universal veil or blematogen 

 layer, as this type of veil has been distinguished by Atkinson (6) . 

 The filaments in this region show very little change in form or 

 structure from those covering the outer portion of the primordium 

 of the basidiocarp. Within this region is one of slightly smaller 

 filaments with thinner walls and richer protoplasmic contents, 

 merging into a less deeply staining region which has undergone no 

 further differentiation. This interior zone of smaller, actively 

 growing filaments marks the primordium of the stipe, which at this 

 stage is somewhat conical in shape. Fig. 52 shows a somewhat 

 older fruit body in 'which internal differentiation has been carried 

 much farther. Here can be seen quite well defined the primordium 

 of the stipe as an elongation of the conical region first difterentiated, 

 and the beginnings of the primordium of the pileus in a very slight 

 enlargement of the apex of the stipe. The hyphae making up the 

 densely staining region marking the primordia of stipe and pileus 

 are smaller, about i . 5 ^i in diameter, and much more closely inter- 

 woven than those of the outer portion, as can be seen in fig. 79, a 

 higher magnification of a part of the fruit body shown in fig. 52. 

 The blematogen and the filaments in the interior show the same 

 characters as those of the young fruit body previously described, 

 except that in the stipe the central filaments have come to lie some- 

 what parallel to each other, extending in a vertical direction. 

 Figs. 54 and 55 show a smaller but older fruit body. The blemato- 

 gen, stipe, and pileus are very clearly differentiated. As can be 

 seen in fig. 80, a higher magnification of fig. 54, the filaments of the 

 pileus are very compactly interwoven toward the interior, but 

 become more and more loosely interwoven toward the margin, 

 where they merge into the blematogen. 



It is interesting to note that the stipe is usually the first region 

 to be differentiated in several other endogenous forms, as in Lepiota 

 cristata and L. seminuda (9), in several species of Cortinarius (15, 



