52 
EXPERIMENTS UPON THE HETERCECISM OF THE 
UREDINES. 
By Charles B. Plowright. 
The 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 sub- 
ject, and who considered 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 ^Ecidium 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 lineans 
followed the infection of the plants with the iEcidium spores ; but 
in no less than eleven of them did the Uredo appear upon the un- 
infected wheat plants kept as control plants * The consequence 
was that my faith in the heteroecismal 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), how- 
ever, a second series of experiments was instituted, which had not 
been long in existence before overwhelming evidence of the 
heteroecismal nature of several species was forthcoming. 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 Pwstelice. Of all heteroecismal 
cultures the easiest successfully to conduct are those in which the 
Podisomce are employed as infecting material ; at least such is my 
experience, although Prof. Fallow has not been so successful with 
his cultures^ in America. On every occasion upon which I have 
infected hawthorns with Podisoma juniperi, and pears with P. 
sabinae , the corresponding Fcestelice have been produced. Now 
both these Roestelice are very uncommon plants near Kings Lynn. 
With Gymno sporangium 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 gramins on barberry were successful, 
the control plants remaining free from the fungus. 
* Plowright, “ Grevillea,” vol. x., p. 40. 
t Farlow, “ The Gymnosporangia of the United States,” pp. 34, 35. 
