174: THE AMERICAN MONTHLY [August, 



tissues are gradually eaten away, so that only a fungal stroma remains, 

 which is closely fused with the surrounding tissues. In no case, ex- 

 cept perhaps in that of the aecidium, is there any apparent disorgan- 

 ization of the functions and arrangement of the sub-epidermal host 

 tissues other than that which arises from a complete or partial appro- 

 priation by the parasite. Parasitism is complete, the attachment of 

 fungus to the host is that of living connection. This ability of fusing 

 with the host tissues, and thus being able to draw direct nourishment 

 therefrom, may perhaps in part account for the lack of true haustoria. 

 Various authors* have spoken of and figured certain branch-like pro- 

 tuberances, which penetrate the cells, as haustoria. In the species I 

 have studied the young mycelia present many such appearances, but I 

 take it that they are simply young hyphal branches which have pene- 

 trated the cell-walls. During the earlier growth they may be found in 

 various lengths and forms, but in older stages the cells will be found to 

 to be penetrated by many not short branches (haustoria) , but continuous 

 filaments, the former being apparently wholly absent. The ability of • 

 these parasites to gradually unite with and dispose of host tissues by 

 solution is probably connected with a power of secreting an unorgan- 

 ized ferment. f H. Marshall Wardj has succeeded in the case of a spe- 

 cies of Botrytis which attacks the lily in separating such a ferment, 

 which is described as having a.macerating effect upon plant tissues. He 

 also ascribes the anastomosing of the hyphae with the consequent solu- 

 tion of the adjoining walls to the same agency. The same power evi- 

 dently accompanies the growing hyphae of the uredines, yet to a 

 perhaps less obvious degree. 



Spermogonia and y^Ecidia. — In the spring, upon the germination 

 of the teleutospores and the formation of sporidia, the yearly life-cycle 

 begins by an infection of the non-glumaceous host by means of the 

 sporidia. These are small protoplasmic bodies which are abscised 

 from the promycelium of the germinating teleutospores (fig. 4) . Though 

 I have made successful cultures by placing the germinating sporidia of 

 Puccinia graminis upon the leaves of the barberry, I have searched in 

 vain to ascertain the method of entrance of the germ tube into the leaf 

 tissues. De Bary,§ the only one who claims td have seen the process, 

 has figured the same as piercing directly through the cuticle. How- 

 ever, in another species, the infection was noted as taking place byway 

 of the stomata,|| and it is, I believe, not improbable that such would 

 most often occur in this case. 



In the case of a barberry bush, upon which I experimented, that had 

 been carefully isolated by being placed in a green-house before it began 

 to open its leaf buds, the spermogonia appeared as yellow spots upon 

 the upper sides of the infected leaves in fourteen days after the applica- 

 tion of the sporidia. 



Vertical cross-sections of the leaf passing through these bodies show 

 them to be pyriform structures, with. their rounded bases sunken slightly 

 in the sub-epidermal tissues of the host, and their apices protruding 

 through the ruptured epidermis. This may, perhaps, be considered as 



* Bagnis, " Obs. Vita et Morphol. Funghi Uredinei ; " quoted from Plowright, I. c, p. 4. 



fSee Vines' Plant Physiology, p. 191. 



% Annals of Botany, vol. ii, p. 319. 



§ Morphology and Biology of the Fungi, p. 280, fig. 128 c. 



11 L. c, p. 284. 



