NUCLEAR BEHAVIOR IN PROMYCELIA 
39 
liminary paper (lo). Galloway (14) studied the germination of the 
aecidiospores in water and noted that the germ tubes which they 
produce may become somewhat septate, but he did not observe the 
production of sporidia and his drawings scarcely suggest a resemblance 
to promycelia. In more than twenty figures Clinton (5) shows the 
various stages of germination which he studied. He also notes an 
occasional septum in some of the tubes, but he did not obtain the 
production of sporidia. Tranzschel (18) and Clinton (6) both claim 
to have established by infection experiments that C. nitens is the 
aecidial stage of Puccinia Peckiana Howe. Tranzschel's experiments, 
however, w^ere not guarded by checks. The data given below show 
that such a connection is very improbable. The wwk of these authors 
has, nevertheless, been accepted and Arthur (i) has made C. inter- 
stitiale Schlecht. (C. nitens Burrill) the type species of his genus 
Gymnoconia Lagerh. This genus is described as autoecious and as 
including in its cycle of development, spermatia, aecidiospores and 
teleutospores. The only other species in the genus is Gymnoconia 
Rosae-gymnocarpae (Dietel.) Arthur. The teleutostage of this species 
is not known and my work suggests that a study of the germination 
of its aecidiospores may show it to be a short-cycled rust with a life 
history similar to that of Caeoma nitens. At any rate it is plain C. nitens 
cannot properly be included under Lagerheim's genus Gymnoconia. 
Olive (16) and Kurssanow (ii) have found that the aecidiospores 
of Caeoma nitens normally contain two nuclei. They have also 
shown that sexual fusions occur in the base of the caeoma, previous 
to the production of spores. The nuclear phenomena covering this 
stage in its life history are well established and agree with what has 
been found by Blackman (2), Christman (4) and others in a rather 
large number of rusts. In my preliminary paper I showed that the 
aecidiospores produce promycelia, but I had not then made a cyto- 
logical study of the nuclear phenomena of their germination. 
The material used in my further studies was obtained from well- 
infected blackberry leaves. The spores were dusted on the surface of 
t tap-water in Petri dishes. In the early spring good germination could 
be obtained in such cultures when they were kept at room tempera- 
ture (about 23° C), but later in the season when the weather became 
quite warm it was necessary to place the cultures on top of an icebox 
in order to secure abundant germination. Most of the spores which 
I have used were taken from leaves of Rubns frondosus that were 
