34 PROCEEDINGS OF THE AMERICAN ACADEMY. 



cells are constantly coming to the level of the rest in the formation of 

 the hymenial layer. Secondary folds arise from the primary ones by a 

 similar process of development which ceases only at the maturity of the 

 fruiting body. A repetition of this folding, which causes the trama to 

 appear branched in section (fig. 7), results in a general enlargement of 

 the gleba while the peridium is pushed farther away from the columella, 

 the gross form of the plant becoming thus changed from almost columnar 

 to broadly clavate. This excessive growth of the gleba causes it to equal 

 or to exceed the columella in thickness within the very thin peridium, a 

 condition presenting a distinct contrast to that of a younger stage, in which 

 the peridium as well as the columella is much thicker than the gleba. 



Little has been said as yet in regard to the growth of the peridium 

 and its conditions at maturity. That it originates from the part of the 

 mycelium which was not differentiated into central axis and gleba has 

 been already mentioned, and also that its development after this differen- 

 tiation is independent of the development of axis or gleba. With the 

 increase in the size of the gleba is associated a corresponding increase in 

 the extent of the peridium, which does not, however, become any thicker. 

 In mature specimens it is exceedingly thin in comparison with the 

 columella, so that at the apex the continuity of the two regions is very 

 inconspicuous (fig. 5) ; and even in so young a stage as that represented 

 in fig. 7, it is only the peripheral hyphae of the columella and of the 

 peridium which anastomose at the apex. The distinction between the 

 two regions about the stipe also is clear in this figure. From the fact 

 that in some mature specimens (fig. 2) the relatively exceedingly thin 

 and delicate peridium is continuous over the gleba, one must assume that 

 its growth has kept pace to a certain extent with that of the elements 

 within it. In a majority of specimens, however, (fig. 3) the chambers are 

 more or less exposed in places, as if excessive growth within had stretched 

 the peridium and finally caused it to become pulled ajoart over certain 

 areas. This condition is probably further accentuated by the irregular 

 wearing of the delicate weft which constitutes the peridium in the older 

 stages ; and in some specimens the honeycombed surface of the gleba may 

 be almost entirely exposed. 



This partially exposed condition of the hymenial region is no doubt 

 connected, in a measure, with the dissemination of the spores, many of 

 which must, in such cases, be discharged directly into the air. Observa- 

 tions made by Dr. Thaxter in the field on abundant material in all con- 

 ditions of development show, however, that with the exception of this 

 limited dispersal from the more or less exposed glebal chambers, no 



