— 137 — 



Eleven infections were made, nine of which were successful, 

 uredo sori being produced in about two weeks, upon one or more 

 of the infected leaflets in each case. 



The two important facts learned from the above experiments 

 are that the uredo spores prefer a low temperature in germination, 

 and merely reproduce the uredo form. 



The Teleutospore Stage, III : This is considered the resting 

 stage in the Uredineae. It was therefore expected that those 

 teleutospores which survived the winter on the dead clover stems 

 would germinate freely in the spring. Repeated cultures were 

 made in the winter and spring, but only seven spores in all germi- 

 nated, and even in these cases the development was soon arrested. 

 This result, so far as this species is concerned, would seem to 

 strongly militate against the generally accepted theory that this is 

 the hibernating stage ; but before any conclusions can be reached, 

 further investigations are necessary. 



The Aecidium Stage, I : — The mature aecidio-spores germinated 

 at all times during the winter and spring. Germination took 

 place most rapidly at a temperature ofi5° — 18° Cent., often begin- 

 ning in from one and one-half to three hours. 26 Cent., was the 

 highest temperature limit of germination. 



Infections with germinating aecidio-spores were made upon 

 young clover plants selected from a large number of uninfected 

 plants grown for the purpose. These experiments were regarded 

 as of chief importance in this study ; for should these infections 

 result in the production of the uredo or teleutospores, the connec- 

 tion of the aecidium with the other two forms would of course be 

 established. From infections with aecidio-spores made in the 

 spring and early summer, uredo sori resulted on one Red and five 

 White Clover plants, the sori appearing on one or more of the in- 

 fected leaflets in each case and upon those leaflets only.* 



*Upon one and two leaves respectively of two other Red Clovers, the sori 

 appeared upon uninfected as well as infected leaflets but not on leaves unin- 

 fected This can be readily accounted for by the fact that the leaflets fold 

 together at night and in this way, the fluid containing the spores could 

 easily have been transfered to the leaflets previously uninfected. 



One White Clover, while producing sori on infected leaflets, also showed 

 them upon one uninfected leaf. As none of the control plants were af- 

 fected, the most probable explanation of this error is that the leaf was acci- 

 dentally infected. 



