55 



according to the system of nomenclature in use at the present 

 time, the name becomes U)'oinyces houstoniatus (Schw.) n. n. If 

 the system of nomenclature proposed by Professor J, C. Arthur is 

 followed, then the name becomes Nigredo lioiistoniata (Schw.) n. n. 



One of the most interesting things in the life history of this 

 rust is that the teleutospores germinate in the living leaves of 

 Sisyrincliijim and probably infect plants of Hoiistonia during the 

 summer and autumn, the mycelium remaining dormant until the 

 following spring when aecidia develop. In so far as I have been 

 able to ascertain, species of Uromyces, whose teleutospores germi- 

 nate in living leaves, rarely have an aecidial stage. 



I have tried several times to inoculate Sisyrinchiuni graminoides 

 with aecidiospores from Hoiistonia purpurea L., both in the field 

 and the greenhouse, but without definite success. Whether the 

 plants were not susceptible at the time the inoculations were 

 made, or whether the Aecidiitm of H. purpurea is not the same 

 as the one of H. caerulea, I am unable to say. I have shown 

 elsewhere* that there is considerable difference in the suscepti- 

 bility of plants to infection by rusts, even the same plant, at 

 different times. I have repeatedly observed a marked difference 

 in the susceptibility of Trifolium pratense L., T. hybridum L., 

 and T. repens L. to infection by Uromyces trifolii (A. & S.) Wint. 

 When one of these was seriously injured by the rust, the other 

 two, growing beside it so that their leaves intermingled, were 

 not affected by the rust. 



Last spring I noticed that there were abundant aecidia on a 

 blue violet growing beside Andropogon virginicus L. having 

 Uromyces andropogonis Tracy on the dead leaves and stems. To 

 test whether the Aecidium was related to the Uromyces, pieces 

 of the rusted grass were collected and taken to the laboratory. 

 The next day the pieces of grass were distributed through five 

 clumps of the same kind of violet. Two weeks later yellow 

 spots began to appear on the leaves of each clump, followed by 

 aecidia. In all probability, aecidia on certain species of Viola 

 have been determined as those oi Puccinia violae (Schum.) DC. 



* Preliminary studies on the rusts of the asparagus and the carnation : Parasitism 

 oi Darluca filmn. Science, N. S. 16 : 397. 235-237. 8 Ag 1902. 



