448 THE AMERICAN NATURALIST. [VoL. XXXIV. 
Nuclear Phenomena in Ustilagineze. — Contributions such as Pro- 
fessor Harper presents! have been few, but are much needed to 
explain this class of plants. He studied, in particular, the germina- 
tion, growth, divisions, and fusions of Ustilago antherarum and U. 
Scabiose. He finds that in fusions of conidia, which are apparently 
caused by chemotactic stimuli, no nuclear changes take place, yet 
the cytoplasmic union of the cells causes them to increase in size, 
and gives them power to resist unfavorable conditions. It may be 
a primitive or degenerate sexual union. J. B. S. NORTON. 
Cell Division in Sporangia and Asci.?— Dr. Harper has contrib- 
uted another very valuable investigation upon the morphology of the 
structures named. Among the Phycomycetes he has studied spore 
formation in sporangia of Synchitrium, Pilobolus, and Sporodinia, 
and for comparison, ascospore formation in Lachnea scutellata among 
the Ascomycetes, in which he was able to find stages undiscernible 
in his previous work on Peziza and Erysiphe. 
In Synchitrium he regards the uninucleated cell as the vegetative 
body of the plant, the supervening multinucleate condition consti- 
tuting, in his view, a sporangium rather than a thallus body. Cleav- 
age by invagination of the plasma membrane follows this multinu- 
cleation, the contents of the “ sporangium ” being segmented, from 
without inward, into irregular plasma masses containing numerous 
nuclei. This cleavage resembles what is seen in some insect eggs. 
The segmentation of the protoplasm does not occur by repeated 
bipartitions or by the formation of walls, simultaneously, about the 
several nuclei. Orientation with respect to the nuclei is not evident 
at first, but becomes apparent later, in the final subdivision of the 
contents of the sporangium into uninucleate plasma segments. A 
shrinkage then occurs, followed by increase in size of these “ proto- 
spores” and the subsequent repeated division of their single nuclei, 
to form from eight to twelve or more in a single “ protospore.” The 
number of them is not definite as in the ascus, but seems to depend, | 
according to Harper, on the individual conditions of nutrition in the . 
different * protospores.” 
Substantially the same cleavage process of spore formation was 
observed in three species of Pilobolus and in Sporodinia. There is 
nothing in the process of spore formation described in the Phycomy- 
1 Harper, R.C. Nuclear Phenomena in Certain Stages in the Development 
of the Smuts, 7rans. Wis. Acad. Sci; vol. xii, pp. 475-498, Pls. VIII, IX. Octo- 
ber, 1899. 2 R. A. Harper, in Annals of Botany, December, 1899. 
