296 THAXTER. 



Xenomyces, Ackermannia and Sphaerocreas ; and numerous other 

 references to the genus Endogone, or descriptions of new species, are 

 to be found here and there in various other pubheations. In the 

 appended list of literature, however, only such titles are included as 

 are in- some measure essential, and those which have reference merely 

 to records of occurrence have been omitted. 



Turning first to the genus Endogone, and following the conception 

 of the genus which has been adopted by Bucholtz and all recent 

 writers, one is forced to include in it all the three categories of spore- 

 forms above enumerated, namely, zygospores, sporangia and chlamy- 

 dospores. In order to avoid new names and combinations I have 

 adopted this procedure as a provisional solution. It may be well to 

 repeat, however, that although the sporangial forms arise in general 

 from a similar vegetative body, and are associated in somewhat similar 

 aggregations in similar habitats, their connection with the other types 

 has not been definitely indicated, even by close association in nature, 

 and their inclusion in the same genus is based on a pure assumption. 

 Whether it may prove desirable to retain the name Endogone for the 

 sexual and chlamydosporic forms and to apply a different name to 

 those which form sporangia is not as yet clear. It may further be 

 pointed out that the presence of isogamy and of heterogamy, of 

 specialized spore envelopes or their absence, as well as of simple and 

 multiple aggregations of the zygospore masses, may similarly lead to a 

 subdivision of the sexual forms themselves, under more than one 

 designation. The desirability or the reverse of either of these pro- 

 cedures will, however, doubtless become more clear as the lacunae in 

 our knowledge of the group are gradually filled. 



The reasons which have determined the selection of the sexual forms 

 as the true representatives of the genus, as originally founded, are 

 based on an examination of the original figures and description given 

 by Link (1808), of the type-species, Endogone pisiformis, on p. 33 of 

 the apparently rare publication in which his paper is contained. The 

 exact wording of this description is as follows : 



" 38. Endogone. Sporangium subglobosum, extus floccosum, intus 

 grumosum sporangiola minuta, globosa, membranacea, sporidiis repleta. 



"Praecedenti generi affine, (Tuber), supra terram in muscis crescit 

 hypothallo radiciformi. Membrana externa sporangii tenuis floccosa. 

 Contextus caeterum vesiculosus, microscopio simplici inspectus 

 grumosus, at compositi ope conspiciuntur sporangiola, ut in prae- 

 cedenti genere, dispersas inter vesiculos multo minores. Sporidia 

 minuta, globosa, sporangiolis inclusa. Unica species. 



