1912] CURRENT LITERATURE 87 



differ from that of S. Junci, but some of the stages appear to be more easily 

 observable in S. graminis. The youngest stages are uninucleate amebae. 

 These fuse to form plasmodia which grow until they occupy the entire host 

 cell. The nuclei of the growing plasmodia all divide repeatedly and simul- 

 taneously in the manner described for other members of the Plasmodiophora- 

 ceae. At the close of the vegetative stage the akaryote or chromidial stage 

 begins. The nuclei lose their contents, leaving only vacuoles in their place. 

 Within these vacuoles apparently fresh nuclei are organized. These undergo 

 mitotic divisions, after which the Plasmodium is broken up by cleavage into 

 small uninucleate masses which become the spores. Under the classification 

 of Maire and Tison, this form would be placed in their genus Ligniera, which 

 includes those species of the Plasmodiophoraceae which lack the schizogenous 

 stage and do not cause swelling on their host plants. — H. Hasselbring. 



Zygopteris. — Scott 2 * has studied sections of a new specimen of Zygopteris 

 Grayi, and finds that it is an Ankyropteris, as Bertrand had pointed out, on 

 the basis of the presence of peripheral loops on the leaf trace. The vascular 

 cylinder of the stem (a 5-rayed star in section) is regarded as "a highly elabo- 

 rated protostele," there being at present no evidence for the existence of a true 

 pith in any member of the group. This is certainly a simpler interpretation 

 of the pithlike region with interspersed tracheids than to regard the cylinder 

 as a " condensed" polys telic structure. It would be even simpler to eliminate 

 "highly elaborated," and to call the cylinder an incomplete protostele. The 

 problematical and abundant "aphlebiae" are found to be "modified basal 



shown bv the structure 



strand."— J. M 



Effect of temperature on respiration. — Kuijper, 30 while at the Buitenzorg 

 laboratories, determined the C0 2 production by seedlings of Arachis hypogaea 

 and Oryza sativa at various temperatures from 15° C. to 50 C. He finds that 

 the effect of temperature on respiration of the tropical plants studied is the 

 same as on plants in the temperate zone. 31 But the "critical temperature" 

 (temperature at which a high respiratory intensity is maintained for a con- 

 siderable time) of Arachis hypogaea is 5°-io° higher than that previously found 

 for Pimm and Lupinus. Kuijper thinks this difference is due to their sur- 



roundings. 



J 



temperature of the vegetation period of the temperate zone. — Sophia H. 

 Eckerson. 



29 Scott, D. H., On a paleozoic fern, the Zygopteris Grayi of Williamson. Ann. 

 Botany 26:39-69. ph. 1-5. fig. 1. 191 2. 



30 Kuijper, J., Einige weiteren Versuche iiber den Einfluss der Temperatur auf 

 die Atmung der hoheren Pflanzen. Ann. Jard. Bot. Buitenzorg II. 9*45-54- P^- 6, f* 



1911. 



31 Bot. Gaz. 50:233. 1910. 



