648 
Journal of Agricultural Research 
Vol. XXXI, No. T 
As the writer interprets Colley’s discussion of the development of 
the uredo sorus in Cronartium ribicola , the “peridium” is the exact 
homologue of the buffer tissue in Gymnosporangium. Certain cells 
of the uredo primordium become oriented vertically, and, by elongat¬ 
ing, develop a thrust against the epidermis. These cells divide, and 
the upper daughter cells* in conjunction with their homologous 
neighbors, constitute the peridium made up of elongated cells. The 
subterminal cells now divide to give rise to spore initials above and 
basal cells below. The telial peridium is evidently developed in 
much the same way. 
It has been found (5) that in several species of Gymnosporangium 
the teleutospores arise from the subterminal cells of the chains, 
composing the primordium. The terminal cells, by swelling and 
elongating, serve as a buffer tissue to break open the overlying host 
tissues. The sacrifice of these terminal cells is made necessary by 
the fact that the tissues above the sorus are very tough, even in the 
case of leaf sori. The substance originally contained in the cells of the 
buffer tissue is not wasted, however. The teleutospore buds, by 
growing up through or between the sterile cells, absorb their pre¬ 
digested disorganization products, just as in all sorts of fungi one sees 
cases of self-parasitism in the form of “ Durchwachsung” phenomena. 
In the uredo sorus of Pucciniastrum ( 12 , 6) the terminal cells of the 
sorus primordium are sterile and, though persisting as a “peridium,” 
first lose their contents, swell and elongate, and function primarily as a 
buffer tissue. Adams (I), in a paper on the Peridermiums, shows 
that the fusing cells are merely intercalary cells in a space making 
buffer complex of parallel hyphae. In deep-seated sori there may 
be a half dozen or more cells above the fusing cells in the chain. 
The writer has found no evidence anywhere in the rusts that these 
chains are multicellular trichogynes. 
Even though a buffer tissue persists more or less, as it does in 
Gallowaya, it should not be confused with a peridium. Morpho¬ 
logically, the latter structure in the rusts, if one is to take the peridium 
of the aecidium as the standard, is composed of spore and intercalary 
cells. In the uredo sorus of Pucciniastrum (6) the buffer tissue may 
be a true peridium, unless Kursanov {12) was correct in his statement 
as to this structure in Pucciniastrum pirolae . He claims that the 
intercalary cells which lie immediately below the terminal cells are 
cut off by the cells below. This would make the “peridium” of 
Pucciniastrum the homologue of the “peridium” of the uredinium 
of Cronartium and of the telium of Gymnosporangium, in neither 
of which is the structure a true peridium. 
There has recently been described (8) a short-cycled strain of 
Caeoma nitens in which no spermogonia are developed. In every 
such case the aecidiospore arising without cell fusion is uninucleated, 
and on germination produces a two-celled promycelium with only two 
sporidia. The fact that Gallawaya develops at most only vestigial 
spermogonia does not seem to be of any particular effect on future 
growth processes. The internal promycelium is four-celled and 
produces at least four sporidia. Lindfors (13) says that in Puccinia 
arenariae , a short-cycled rust, the teleutospore produces a two-celled 
promycelium. Cell fusions do not occur in the sorus, the cells of the 
mycelium being already binucleated. A nuclear fusion in the 
spores is followed by two divisions, but the septa which divide the 
