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From the preceding experiments the important fact was estab- 

 lished, that the secidiospores through their germination and sub- 

 sequent mycelial development within the host, give rise to uredo 

 spores ; settling one of the principal questions involved in this 

 study. 



SUMMARY. 



i. The parasitic Clover Rust is chiefly propagated throughout 

 the growing season of the host, by the Uredo spores, owing to 

 their abundance, rapid germination, and the fact that for the most 

 part, the) 7 reproduce only their own form of spore. 



2. The germination of the secidiospores gives rise to uredo sori, 

 thus demonstrating, what has heretofore been merely assumed, 

 viz : the connection of the aecidium or "cluster-cup" of Clovers 

 with the brown ' ' Clover Rust. ' ' 



3. Both uredospores and secidiospores prefer a low temperature 

 in germination. This accounts for the fact that during the mid- 

 dle period of the summer of 1890, which was very warm, little of 

 the Rust appeared, while more of it was generated during the 

 later and comparatively cooler months, although at no time did 

 the amount equal that produced during the cool and moist mid- 

 summer and autumn of 1889. 



The most important questions remaining to be investigated, in 

 the life-history of the Clover Rust are its mode of hibernation, 

 and the origin of the secidia. The two questions are closely 

 linked together, and two theories have occurred as possible solu- 

 tions of them. First, the aecidia may be produced in the spring 

 through the germination of teleutospores which live over winter on 

 the dead clover stems. Second, the uredo and teleutospores may 

 germinate in the fall, form mycelium in the White Clover plants, 

 and survive the winter in them as mycelium and spermogonia. 

 The first mode would seem the natural one for preserving the para- 

 site through the winter ; but the small number of germinations ob- 

 tained from the teleutospores taken from the dead stems implies 

 some other mode of hibernation. The second theory is supported 

 by the fact that in 1890 at least, not only the secidia, but mainly 

 the uredo and teleutospores also, were found in spring and early 

 summer, occurring mainly on the White Clover. The infection 

 of the "rowen" or second crop of Red Clover evidently took place 

 largely through the generations of uredospores derived from the 



