372 THE AMERICAN MONTHLY [Dec 



The uredospores continue to propagate the nredo form of 

 the fungus indefinitely upon the wheat, but the teluto- 

 'spores or sporidia arising from them will only grow my- 

 celia if sown on the leaves of the berberry. 



In not a few instances these relationships have been 

 established by direct experiment. Dr. C. B, PlowrigliL 

 succeeded in producing aecidia on the hawthorn and 

 mountain ash by infecting their leaves with telutospores 

 taken from the juniper, and on the nettle with teluto- 

 spores from a species of Carex. Conversely, with aecid- 

 iospores from the nettle he obtained the uredospores of 

 Pnccinia caricis on Carex, and spores from the colt's-foot 

 cluster-cup placed on the meadow grass developed tiie 

 uredo form of P. forariim. The aecidium of the berberry 

 gave rise to P. graininis on grass, and berberry loaves in- 

 fected with telutospores from the latter developed 

 aecidia of the usual form. Check plants which in these 

 experiments were not inoculated yielded negative results; 

 the possibility of error was thus eliminated. It may 

 therefore be taken as conclusively proved that many of 

 these leaf fungi exist in alternate generations as para- 

 sites on distinct plants, with forms so unlike that the suc- 

 cessive phases in the life cycle of one and the same fun- 

 gus were long regarded as different species and classi- 

 fied in separate families. The brilliant orange and scar- 

 let tints exhibited by so many Uredines are due to the 

 presence in their cells of drops of highly-coloured oil. 

 They differ from the Peronosporea? in their sejjtate mycel- 

 ium, and are less destructive, as the mycelium does not 

 extend through the entire body of the host, but the dam- 

 age i.s usually restricted to the small aflected areas of the 

 leaf. Sexual reproduction has not been observed in the 

 Uredines; there are, however, grounds for the belief 

 that a process of fertilization really takes place, but the 

 consideration of this question must be reserved for an- 

 other occasion. — Knowledge. 



