272 
EXPERIMENTS UPON THE HETERGCISM OF THE 
UREDINES. 
By Mr. Cuartrs B. PLowricHr. 
Tuer following thirty-five experiments are a portion of two series of experimental 
cultures conducted during the years 1881 and 1882 upon the physiology of the 
Uredines. They are published at the request of several of my friends who are 
interested in the subject, and who consider further evidence upon the phenomena 
of hetercecism desirable. It may be observed that the species with which these 
experiments were commenced, and which was the prime cause of their performance 
at all, was the Zcidium upon Berberis vulgaris. In the summer of 1881 a number 
of cultures were made with the spores of this fungus upon wheat; the result 
obtained was that in twelve out of thirteen of these experiments Uredo linearis 
followed the infection of the plants with the cidium spores; but in no less than 
eleven of them did the Uvedo appear upon the uninfected wheat plants kept as 
control plants.* The consequence was that my faith in the hetercecismal character 
of this species was so much shaken that I was hardly able to believe in it at all. 
During the spring and summer of the present year (1882), however, a second 
series of experiments was instituted, which had not been long in existence before 
overwhelming evidence of the hetercecismal nature of several species was forth- 
coming. In these cultures various and less common Uredines were employed, so 
that the error of accidental sporadic infection, it is scarcely possible to believe, 
could have taken place time after time, with species after species. To take, for 
instance, the Restelie. Of all hetercecismal cultures the easiest successfully to 
conduct are those in which the Podisome are employed as infecting material ; at 
least such is my experience, although Prof. Farlow ha not been so successful with 
his cultures} in America. On every occasion upon which I have infected haw- 
thorns with Podisoma juniperi, and pears with P. sabinw, the corresponding - 
Restelia have been produced. Now both these Restelie are very uncommon 
plants near King’s Lynn. With Gymnosporangium juniperi upon mountain ash, 
four out of five cultures were successful, which is the more noteworthy when it is 
remembered that the Gymnosporangium was sent from Forres, in the north of 
Scotland (some 400 miles away), by my friend the Rev. James Keith, it being a 
plant that does not grow in this district. 
All the cultures of Puccinia graminis on barberry were successful, the control 
plants remaining free from the fungus. 
With Acidium berberidis on wheat the three experiments performed were all 
entirely successful, the check plant remaining free from the fungus. Both the 
infected and the control plants in these last-named experiments were raised under 
= Plowright, Grevil/ea, vol. x., p- 
i Farlow, The Gymnosporangta of oe United States, pp. 34; 35+ 
