1896-97.] THE GAMETOPHYTE OF BOTRYCHIUM VIRGINIANUM. 27 



Leitgeb'^ in the prothaWia of Pten's creh'ca, AsJ>zdm7H/a/mtujn, and other 

 ferns ; the formation of the dark brown sheath from the cell-wall of the 

 host-plant being very characteristic. Atkinson'"' has described a similar 

 phenomenon for a Conipletoria found in the same species of prothallia 

 in America. In the filamentous portion of the undivided mycelium as 

 well as in the formation of its conidia it markedly resembles a Pythium. 

 In the botryose vesicular masses completely filling the cells of the host, 

 it again strikingly simulates Completoria. It may perhaps fairly be 

 considered as a form uniting the genera Pythium and Completoria. If, 

 on further investigation, the above view proves to be correct, it may 

 possibly be necessary to remove Completoria from the vicinity of the 

 EntomopthoraccE, where it has been placed on account of its ejaculatory 

 conidia by Nowakowski and Thaxter, and toreplace it with the Perono- 

 sporacece where Leitgeb, as a result of his careful investigation, con- 

 sidered it to belong. 



The endophyte of the prothallium of Botrychium virginianum , unlike 

 that of Lycopodium cernuum, described by Treub.'^ and that of L. 

 annotinum, described by Bruchmann,'^ is always intracellular and never 

 becomes intercellular, in the deeper layers of the host-plant. Treub's 

 description is somewhat brief, but from the fuller account of Bruchmann, 

 the structure of the mycelium in the symbiont of Lycopodium seems to 

 be quite different from that of the form found in Botrychium virginia- 

 num. 



Only further study of the fungus can settle whether it is a distinct 

 species of Coinpletorta or Pythium, or, on the other hand, an intercalary 

 species. Before leaving this subject, there is one more interesting fact 

 to record. . In older prothallia bearing well-advanced sporophytes, the 

 symbiont is shrunken and dead. Whether this state of affairs is rightly 

 comparable to the similar phenomena observed by Frank in the 

 mycorhizce and mycodomatia of various Phanerogamia, at the time of 

 flowering or seeding, and is to be considered as a digestion of the sym- 

 biont by its host, must for the present be left in suspense. The 

 prothallia often continue to live long after the death of the endophyte. 

 Nothing of the nature of an oogonium has yet been observed in any stage 



of development of the fungus. 



VI. 



The antlieridia arise, after the first basal cluster has been formed, figure 



12. Sitzuiigslierichtud. AkaJ. d. Wissch. Wien. Math.— Natwissch. Classc. Bd. 84. Abth. i., 1881, 

 p. 291 and p. 307. 



13. Bull 94. Cornell Experimental Station, p. 52, 53. 



14. Op. Cit. i., p. 124. 



15. Op. Cit. pp. 310-313. 



