388 BOTANICAL GAZETTE [MAY 
cell, which bears an abortive trichogyne-like organ. According to CHRISTMAN,’? 
on the other hand, in the caeoma of Phragmidium speciosum we have the conjuga- 
tion of two equally differentiated cells. BLACKMAN, therefore, believes that a 
heterogamous condition obtains, while CHRISTMAN describes an isogamous one. 
In the subsequent papers of these two authors this essential difference is still 
manifest (see BLACKMAN and FRaAseErR,'® CHRISTMAN’?), In a more recent 
publication, OxrvE?° compares these differences and takes a middle ground, 
believing that both BLACKMAN and CurisTMAN are in particular cases right. In 
four forms of the same caeoma type as Phragmidium, OLIvE finds that the cells 
conjugate as described by CHRISTMAN, but that one is larger than the other, that 
is, a male and a female cell conjugate, the male cell lying a little below the female, 
which is always surmounted by a trichogyne-like abortive cell, while the male cell 
has no such abortive portion. During conjugation a broad opening may be present 
between the two cells, allowing the protoplasmic contents to mix, as described by 
CHRISTMAN, or only a narrow opening between the two cells may be present, 50 
that only the nuclei of the male cells pass into the female cells, a condition which 
OLIVE believes to agree with BLACKMAN’s description. The two phenomena may 
be observed in the same plant. Ourve thus seeks to harmonize the views of 
BLACKMAN and CHRISTMAN. 
Kurssanow has investigated a caeoma, which he found growing on Rubus 
saxatilis near Moscow, and which he regards as the same or a very similar form 
to the caeoma studied by Curistman. He regards CHRrisTMAN’s studies as too 
brief to be conclusive, and endeavors to extend the observations. The cells of 
the vegetative hyphae and haustoria are uninucleate, the nuclei being comparta- 
tively large and distinct. Numerous spermatogonia are present on both surfaces 
of the leaves, whose origin and development are described, with the result that the 
cells are always uninucleate. The caeomas appear only on the under sides of the 
leaves. The formation of a sort of palisade arrangement of uninucleate large - 
terminal cells as described by CHRISTMAN is also described by Kurssanow. There 
is a conjugation in pairs of these cells, which he regards as equal in size. There 
is no condition found which could be made to agree with Oxive’s description, 
but his account is in complete harmony with Curistmay’s results. The ditier 
ences in the methods of conjugation as described by BLACKMAN, CHRISTMAN, and 
OLIVE, this author believes may be due to differences in the forms investigated 
"7 CHRISTMAN, A. H., Sexual reproduction in the rusts. Bot. GAZETTE 39:207- 
274. 1905. 
18 BLACKMAN, V. H., AND Frazer, Miss H. C. I., Further studies on the sexuality 
of the Uredineae. Annals of Botany 20:35-48. 1906. 
10 CHRISTMAN, A. H., The nature and development of the prim 
Trans. Wis, Acad. Sci. 25:517-526. 1907; Alternation of generations and the mor 
phology of the spore forms in the rusts. Bot. GAZETTE 44:81-101. 1907 
20 OLIVE, E. W., Sexual cell fusions and vegetative nuclear divisions 
Annals of Botany 22:331—360. 1908. 
ary uredospore- 
in the rusts. 
