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flesh is very obvious when a thin section of the cap is examined under 

 tho microscope, but in certain genera, as Russii/a and Lacfiirius. many 

 branches of the l.uf/hi become greatly enlarged, forming little vesi- 

 cles or bladders. These vesicles lie in groups all through the flesh 

 of the pileus, sometimes forming the greater part of its substance. 

 The filamentous //vpl.hv pass around and through these groups, filling 

 up the interstices. In cross section this tissue resembles parenchyma, 

 and appears as if it were made up of rounded cells. Such a trama is 

 said to be vi'sicii/ose to distinguish it from the ordinary or floccose 

 trama. The threads on the outer surface of the pileus constitute the 



Figure 212 



Portion of vesiculose trama in the pileus of a 

 Russula. 



Figure 213. 

 Portion of a floccose trama. 



cortex or cuticle. They are thick walkd and often contain coloring 

 matter which gives the plants their characteristic color. In many 

 species their walls become gelatinized, covering the outside of the 

 pileus with a \iscid, slimy, or glutinous layer, often called /v///W^. 

 in other instances the cortical layer ceases to grow with the pileus. 

 It is then torn and split by the continued expanding of the rest of the 

 plant, and remains on the surface in the form of hairs, fibers, scales, 

 etc. 



As an example of the most usual form of the pileus, we may take 

 that of the common mushroom (^Agjricus lampes/ris) when it is nearly 

 expanded. The pileus is then quite regular in outline and evenly 

 convex (Fig. 216). Many mushrooms during the early stages of 

 their development have this form, which is variously changed by later 



