l8 HUMPHREY 



In many cases a complex of hyphge over-runs the surface of a 

 leaf and it is not uncommon to find chlam3'dospores in connection 

 with these external hyphae. One-celled conidia are abstricted 

 in large numbers from branches of the external hyphae. Sclerotia 

 have not yet been found, though occasionally a cell may be seen 

 well filled with knots of hyphse, too loose in structure, however, 

 to be regarded as sclerotia. Cells in which these knots occur 

 are always dead and apparently empty. 



The fungus behaves toward the host as a parasite. Its hyphae 

 produce haustoria in great numbers which in the course of time 

 invade all the cells of a leaf, thus impairing greatly its ability to 

 elaborate food materials. The younger leaves of the host are 

 apparently uninfected, and even though the older parts of the 

 thallus may be dead, growth continues at the growing point and 

 the plant may grow indefinitely, though very evidently diseased. 



The writer has not thus far observed a fungus associated with 

 our species of Sfhmrocarfus or with Tai-gio7iia hypophylla, 

 although Golenkin ^ reports the existence of an endotrophic 

 mycorrhiza for the latter, and it may be that further investigation 

 will demonstrate the presence of a fungus in Targwnia as we 

 find it here. As a matter of fact it is not improbable that all 

 the hepaticse of this region may on further study prove to be 

 infected, the fungus being either a symbiont or, what is more 

 likely, a parasite. The writer has seen no evidence in favor of 

 the view that the fungus stimulates the growth or in any way 

 benefits the host, though the presence of hyphae may lead up to 

 the development of abnormal structures such as modified root- 

 hairs, enlarged cells, etc. 



Bruchmann,^in his studies on Botrychium hinarz'a, concludes 

 as follows : " Der physiologische Nutzen des Zusammenlebens 

 von Prothallium und Pilz scheint mir auch hier nicht darin zu 

 bestehen, dass die w^enigen .und unscheinbaren Pilzfaden, 

 welche aus dem Substrat des Gamophyten in ihn emmiinden, 

 belanglose Humusstoffe ihm zufiihren, Sondern nur darin, 

 dass die von den functionsfahigen Rhizoiden der wachsenden 

 Schutelpartie aufgelosten und herbeigefiihrten Baustoffe mit- 



^Loc. cit., p. 209. 

 ^ Loc. cit. 



