214 BOTAMCAL GAZETTE [September 



considered as a " primary universal veil" or protoblem, 2 such as 

 occurs in addition to the blematogen over the surface of young 

 buttons of Agaricus campestris. It does not, however, show as a 

 definite layer in buttons younger than the one shown in fig. 71, 

 although there are hyphae more deeply stained and with larger 

 diameters at the surface in some (fig. 70). The irregularity of the 

 latter would seem to indicate that they are the ends of hyphae 

 undergoing disintegration on account of their contact with the 

 soil. No trace of a protoblem was found in the four other species. 

 This of course may be due to the fact that it was washed off during 

 the rather vigorous treatment necessary to remove the grit particles, 

 but it hardly seems possible that no trace would be left had it 

 existed. The envelope of interwoven fibrils persists in /. geophylla 

 (pi. XXII) in the oldest stages collected, and forms here the outer 

 portion of a duplex universal veil such as was described in Corti- 

 narins anfr actus and C. armillatus (9). From this loose fibrils 

 arise (fig. 79). Within is a looser, much more delicate tissue with 

 large air spaces. The latter becomes more or less concrete with 

 the pileus at the apex of the fruit body, and shows most clearly 

 between the pileus margin and the stem below the gill cavity. 



Primordium of hymenophore. — Following the differentiation 

 of the stem and pileus primordia, or possibly proceeding at the 

 same time in /. infelix (fig. 21), the fundament of the hymenophore 

 makes its appearance (figs. 3, 4, 16, 19, 22, 23, 35, 36, 40, 41, 47, 

 48, 72, 73). The hyphae in the annular furrow left between the 

 pileus and stem multiply very profusely and turn perpendicularly 

 downward from the more laterally directed fibers of the pileus 

 trama. They become very rich in protoplasm, as shown by their 

 propensity for stain. They are very slender, with more or less 

 pointed ends, so that they are able to push their way easily through 

 the ground tissue. Such a rapid increase in growth here, while 

 practically none is taking place in the blematogen, brings about a 

 stretching and finally a rupturing of the latter tissue, bringing 

 about the formation of the annular cavity (figs. 3, 4). Usually a 

 well defined annular cavity does not make its appearance until 

 the fruit body is slightly older and the palisade layer is organized 



2 See Atkinson (2, 3) for a definition of this term. 



