MICHIGAN ACADEMY OF SCIENCE. 139 



on the ure(l()S])ores of this rust. The first two weio nol very con- 

 clusive ns the iiiaterijil w.is not very ^<»(»<1. A sli<iht <;erniination 

 took place at all temperatures from 10-.S0° C. and no <;ermiuation 

 took i>lace above this. The third series <.ave 21% at 10° C, 42% 

 at 18° C, 20%^ at 24° C, and 0% at 'M)° C. This, as well as the 

 previous two series, indicates a low liuiit for the uiiuimum. 



Pncrinia jxtlijf/diii I'crs. Tlie uredospores of this rust Avere tested 

 three days after jiatherino-. At this time, they did not give a very 

 hioh per cent of oennination. There was no gemiination at 15° C, 

 a slight oerniination at 18° C, while only a few spores germinated 

 at 28° C. and there was no germination at 36° C. 



JJromyccs trifolii (Hedw.) Lev. The uredospores of this rust 

 gave 2% germination at 10° C, 27% at 10° C, 12% at 22° C, 

 and no germination at 34-38° C. 



Colcosporium solklaglnis (Schw.) Tlium. The uredosi)ores of 

 this rust gave rather variable results. At the best, they gave only 

 a small jier cent of germination and, in two out of six series of 

 tests, no germination was obtained at any temperature. In the 

 other four series, a slight germination took place between 14 and 

 20° C, the liest being 13% at 16° C. At other temperatures above 

 and below this, no germination was obtained. It may be that this 

 is one of the rusts which needs the presence of the host in order 

 to bring about abundaut germination, as Freeman found in the case 

 of some races of Piiccinia dispeisa Erikss. on some of the bromes." 



Melampsora Bigloirii Thtim. In two series of tests with the 

 uredospores of this rust, a slight germination took place between 

 10 and 27° C. Above this, there was no germination. In the third 

 series, better germinating spores were used. This gave 14% at 

 10° C, 24% at 16° C, 15% at 22° C, and 0% at 34° C. 



Melampsora Medusae Thfim. The uredosjwres of this rust gave 

 2% germination at 10° C, 6% at 16° C, 0% at 22° C, and 0% 

 at 34° C. 



Cronortium comptoniae Artli. The uredospores of this rust gave 

 no germination. This was probably due to the fact that they were 

 old, since they were collected late in the summer after a long dry 

 spell and the teleutosporic cohrmns had formed in large nund)ers. 

 The aecidial stage of this rust, PGridcrniium comptoniae (Arth.) 

 Orton & Adams, from Western Yellow Pine, gave no germination 

 at 10° C, a slight germination at 18° C. and at 26° C, and no 

 germination at 20° C. 



The germination of tlie teleutospores of the three following rusts 

 were studied: — Cronartiun comptoniae, Cronartiiim commaiulrae, 



9. Annals of Botany 16 :487. 



