138 SEVENTEENTH REPORT. 



in liaiif>iii<i' drops on the cover of a petri disli used as a moist- 

 chamber. These cultures were run for twelve hours and then the 

 per cent of germination was calculated. Most of the work y:hs 

 done upon uredospores but a few teleutospores and aecidiospores 

 were tested. 



Pitccinia coraiKifd Corda. { PiKcinid coionifera Kiel).; Puccinia 

 rhumm'i (Pers. i AVettst. ) The results obtained Avith this rust agree 

 with those obtained by other workers. The uredospores were used 

 and gave 0% germination at 10° C. in two series of tests, 16 and 

 13% at 15° C, 81 7f germination at 18° C, and no genuination 

 was obtained at 80° C. Another series of tests was run, in which 

 spores of diflferent maturity and solutions of different sorts were 

 used. It was found that, in case the spores were taken from 

 pustules on leaves which had been dried for some time, the germina- 

 tion (35% at 18° C.) was much less than when the spores were 

 taken from well opened pustules on green leaves (55% at 18° C). 

 Spores taken from unopened ])ustules on green leaves gave only 

 slight germination at 18° C. There was found to be practically 

 no difference between germination in conductivity water and in 

 ordinary distilled water. In cases where pieces of the host were 

 placed in The hanging dro]> there was no effect obserA'ed, either 

 upon the germination or upon the direction taken by the germ tubes. 

 It was found however that in cases where the cultures Avere illumi- 

 ated from one side that the germ tubes turned away from the light. 

 This negative heliotropism has been reported by Fromme^ for this 

 same rust (Puce. rJiaiimi). The per cent of germination in this 

 series accord with those in the other. A slight germination was ob- 

 tained at 12° C, 15-20% at 13° C, 35-55% at 18° C, 26-46% at 25° 

 C, and very slight germination at 30° C. 



Puccinia taraxaci Plow. The uredospores of this rust gave rather 

 varying results. In one series, no germination was obtained at any 

 temperature. In another, 0% was obtained at 10° C, 1% at 18° C, 

 0% at 27° C, and 0% at 35° C. In a third series, 34% germina- 

 tion was obtainetlj at 10° C. 30% at 14° C, 5% at 18° C, 0% at 

 27° C. and 0% at 35° C. The results obtained would indicate that 

 a rather low temj^eratnre was necessary for this rust. 



Pucciiim sorffhi Schw. The uredos})ores of this rust gave 0% at 

 10°C., 26% germination at 14°C., 50% at 18° C. 247r at 27° C, 

 18% at 35° C, and 0% at 45° C. This shows a hipfher range for the 

 maximum than in most rusts. The most germination however takes 

 ]>lace, as in most other rusts, at about 18° C. 



Pucciriki pMei'pratensis E. &; IT. Three series of tests were run 



Anicr. .Tour. Bot. 2 :82. 



