REVISION OF ENDOGONEAE. 331 



thick-walled, slender, intricately interwoven aseptate hyphae above 

 mentioned, which form the second element of the mycelial crust, or 

 stroma. How these wefts at first originate, it is not possible to de- 

 termine from the material; but as they develop, a distal portion is 

 distinguished from a basal, which forms a very short stout stalk, 

 usually broader than long, but variably developed in different cases; 

 and the broadening distal portion organizes the sporocarp proper. 

 In this process the latter becomes differentiated into a central region, 

 or columella, continuous with the stalk, and surrounded by a sporo- 

 genous layer from which the long oval to somewhat wedge-shaped or 

 subclavate thick-walled brownish yellow spores diverge radially; 

 lying side by side in a single layer which completely surrounds the 

 columella, except in the basal region, where it remains continuous with 

 the stalk (Fig. 83). A section of the sporocarp in this condition sug- 

 gests a mushroom "button" in general outline. 



The sporogenous layer, which occupies the surface of the columella, 

 is thin and somewhat more dense. The spores, which radiate from it 

 with great regularity, are rather uniform, with somewhat flattened 

 extremities, and are attached by a pointed base, which is usually 

 distinguished by a small well defined septum from its origin in the 

 sporogenous layer (Fig. 85). Owing to the confused structure of the 

 branching, densely woven elements which form the sporogenous layer, 

 it has not been possible to determine the exact nature of these origins. 

 Even in thin sections, I have been unable to determine satisfactorily 

 such a simple and continuous relation, between the spores and the 

 hyphae of the columella, as is shown by the figure of Patouillard in 

 this species; or in that of S. coremioides drawn by Weese, in von 

 Hohnel's Fragmenta, No. 174, fig. 1; which appears to be some- 

 what diagrammatic. Although it is not impossible that some form of 

 conjugation may occur in this layer, which is hidden by the confusion 

 of cut ends, loops and convoluted branches, I have seen nothing in the 

 dried material that could be thus interpreted. The thin-walled spores 

 with their basal septum suggest a resemblance to the corresponding 

 type in Endogone illustrated by E. fulva. It may be said in this con- 

 nection that the extraordinary definiteness of the spore-relations is not 

 such as one would expect in a chlamydosporic type; but might possi- 

 bly be interpreted as a higher development of the tendency to segre- 

 gate somewhat specialized spore-groups, which has been above de- 

 scribed in certain sexual species of Endogone, like E. multiplex or E. 

 tuberculosa, and in the chlamydospores of E. vesiculifera and E. fascicu- 

 lata. 



