RUST OF ANTIRRHINUM. 47 



Experiinents on Germination of Teliosfores. 



Numerous attempts to germinate teliospores were made with fresh 

 material, dried material, teliospores produced under glass, teliospores 

 produced outside, and teliospores wintered over outside. These germina- 

 tion tests were made at 7° C, 10° C, 12° C. and 20° C, but in no case did 

 the teUospores germinate. These spores had formed in response to the 

 definite stimulus of cold or drying. They do not germinate when first 

 formed; the}^ are spores of regeneration, and they may be considered as 

 requiring a rest period, like other spores which function to carry fungi 

 through adverse conditions. But these teliospores do not germinate after 

 the rest period, that is, after passing the winter out of doors, when sub- 

 jected to the range of temperature in which their host normally grows. 

 It is not unlikelj^ that they are killed by the cold, not being able to wdth- 

 stand the rigors of the winters to which their host has been carried. 



Peltier {loc. cit.) reports that all efforts to germinate the teliospores 

 failed. 



The fact that teliospores do not germinate may be explained in another 

 way. The temperature-germination curve for urediniospores is very 

 sharp; and if teliospores have an even narrower range of temperature 

 through which they can germinate, it is possible that the right tempera- 

 ture for germination has not yet been hit upon, since a variation a few 

 degrees above or below the optimum temperature would result in no 

 germination. 



According to our present knowledge the teliospores are not only rare, 

 but they do not germinate. This being the case, the possibihty of an 

 alternate host is eliminated. But no alternate host is necessary for a 

 rust fungus which passes the mnter under glass. The chrysanthemum 

 rust fungus (P. Chrysanthemi Roze.) in America dispenses with both an 

 alternate host and teHospores (Atkinson, 1890). Yet this rust occurs both 

 in the greenhouse and out of doors, and persists from year to year. P. 

 Chrysanthemi also is independent of the other rusts found on nearly related 

 Compositse, just asP.Antirrhini is not a parasite on other Scrophulariaceous 

 plants, such as Linaria (see below, experiments with Linaria) . Carnation 

 rust, Urotnyces Caryophyllinus (Schrank) Wint. has an alternate host, 

 Euphorbia gerardiana, in Europe (Fischer, 1910), but it has not been 

 found on an alternate host in this country. If the teliospores of P. 

 Antirrhini ever were functional they seem now to be useless. The uredinio- 

 spores of this fungus are sufficient to propagate it through the year, as long 

 as greenhouses in the vicinity shelter the host plant during the winter. 

 The urediniospore is a spore of dissemination. Spores of regeneration, 

 such as tehospores, are not a necessity for a fungus the host of which 

 occurs both under glass and out of doors. 



The original host of P. Antirrhini is not known. Blasdale (loc. cit.) 

 concluded that either snapdragon rust originated on the wild form of 

 Antirrhinum (.4. vagans), or its original host plant was not a member of 

 the Scrophulariacese. Peltier {loc. cit.) made cross inoculations with 



