SELECTED CYCLES IN GYMNOCONL4 PECKIANA 
83 
that when comparatively low temperatures prevail during the period 
of germination of the aecidiospores, Pucchiia peckiana would be more 
abundant, other conditions being equal, and conversely there would 
be a scarcity of the teleuto stage during years when the temperatures 
in June and early July were comparatively high. 
It will be readily seen that the lack of fixity of the generation cycle 
in Gymnoconia peckiana has an important bearing on the principle, 
recently adopted by some uredinologists, of recognizing the different 
generation cycles as representing distinct generic concepts. Accord- 
ing to the usual practice, which is also in conformity with the Inter- 
national Code, the Gymnoconia peckiana would apply not only to the 
species in its two-generation cycle, but also in its one-generation cycle. 
For the aecidial stage alone, if one desired to employ a name which 
would not include the concept of the teleutospore stage, we have the 
form species name, Caeoma nitens Schw. (or Caeoma inter stitialis 
Schlecht.). Common practice as well as the International Code per- 
mits this use and there is no necessity for a new generic name to apply 
to the one-generation form of Gymnoconia peckiana. 
One of the recent practices in uredinology which has many followers 
in the United States, and which leads to unnecessary confusion, is 
the new nomenclature applied to the spore conceptacles, or spore 
pustules, and also to the spores. According to this new principle, 
the criterion of morphological structures is not their forms nor place 
in the cycle, but their cytological behavior. It is always very clear, 
on the basis of the morphological principle, what the aecidia, or aecidio- 
spores, of Gymnoconia peckiana are, and the same is true of the teleuto- 
sori and teleutospores. On the basis of the new or cytological principle, 
the morphological aecidium becomes a cytological aecium at com- 
paratively low temperatures, but at comparatively high temperatures 
it becomes a cytological telittm, or rather a cytological aecidioid telium. 
Department of Botany, Cornell University 
LITERATURE CITED 
Arthur, J. C. Orange rusts of Rubus. Bot. Gaz. 63: 501-515. 191 7. 
Kunkel, L. O. The production of a promycelium by the aecidiospores of Caeoma 
nitens Burrill. Torr. Bot. Club Bull. 40: 361-300. Fig. i. 1913. 
Nuclear behavior in the promycelium of Caeoma nitens Burrill and Puccinia 
peckiana Howe. Am. Jour. Bot. i: 37-47, pi. 3. 1914. 
Tranzschel, W. Culturversuche mit Caeoma interstitiale Schlechtd. ( = C. nitens 
Schw.). Hedw. 32: 257-259. 1893. A preliminary notice was published in 
the St. Petersburg Naturforscher Gesellschaft in 1892. 
