162 
IOWA ACADEMY OF SCIENCES, 
INOCULATION EXPERIMENTS WITH GYMNOSPORAN 
GIUM MACROPUS LK. 
BY P. C. STEWART AND G. W. CARVER. 
The family of true rusts, Uredineso, is very interesting to 
the mycologist and important to the agriculturist. It contains 
about twenty- seven genera and a multitude of species, all of 
which are strict parasites, living within the tissues of their 
hosts. Several of the species produce destructive diseases in 
cultivated plants; as examples note the rust of wheat, oats and 
other grasses {Puccinia graminis, Pers.), blackberry rust 
[Cceoma luminatum, Schw.), and carnation rust (Uromyces 
caryophyllinus [Schrank], Schroeter). Thus far all attempts 
to cultivate the rusts upon artificial media have failed. Conse- 
quently the life histories of some species are imperfectly 
known. The determination of the life histories of some species 
is made still more difficult because of the fact that they do not 
complete their development upon a single species of host- 
plant, but inhabit different species at different stages in their 
development. The life history of the common wheat rust, 
Puccinia graminis, so frequently used to illustrate this peculi- 
arity of rusts, is so familiar to readers of botanical literature 
that it is unnecessary to repeat it here. It is sufficient to state 
that wheat rust has three stages, two of which are fouad upon 
the wheat or some other grass plant and upon the common 
barberry {Berheris). 
The species of Gymnosporangium belong to this class of 
pleomorphic rusts. There are two forms, representing two 
stages in the development of the fuDgus. Until about ten 
years ago these two forms were supposed to be distinct species 
and were given separate names. The Gymnosporangium form 
(considered to be the higher form) inhabits, exclusively, 
species of the Cupressinem, a group of the family of cone bear- 
ing trees, Coniferm. The other form has received the name 
