1911] CURRENT LITERATURE 79 
the vegetation with different conditions in the different strata. In vegetation 
with an average height of five feet, the average rate of evaporation above the 
herbage, about the middle of it, and in the lower strata, was according to the 
ratios 100:32.8:6.6. Similar vegetation about two feet high gave correspond- 
ing ratios of 100:56.2:14.7. These ratios are valuable indications of compara- 
tive humidity within the vegetation and upon its surface. Temperature 
readings showed that the upper layers of the vegetation were exposed to a 
greater daily range of temperature than either the free air above or the lower 
layers of the vegetation. As the different species vary much in their average 
height, it will be seen that few species of plants forming the marsh vegetation 
have to face precisely the same set of physiological conditions, hence xero- 
phytic and non-xerophytic marsh plants may grow side by side, each in the 
different conditions suited to its requirements——Gro. D. FULLER. 
Catalase.—ROSENBERG” attempts to settle the question whether catalase 
belongs to the anaerobic or aerobic respiratory enzymes. She finds it in great 
abundance in seeds and seedlings showing low anaerobic and high aerobic 
respiration. In yeast it decreases with fermentative activity. In seeds i 
increases as germination progresses. Acids and most salts markedly diminish 
greatly increase it. From these facts she concludes that catalase belongs to 
the aerobic respiratory enzymes. There are two serious criticisms that must 
be offered against the work. The destructive effect of acids on catalase and 
the rapid development of such acids in dead plant tissues is well established. 
Her methods apparently entirely overlooked these facts. It is probable, 
therefore, that she was measuring only a fraction of the entire catalase, and 
therefore that her determinations were open to large error. Again, her con- 
clusion is rather sweeping for the data at hand. Biology can gain nothing 
from such guessing on the basis of questionable data.—WILLIAM CROCKER. 
Embryo of Welwitschia.—Prarson™ has added to his former studies of 
Welwiischia a brief account of the development of the embryo proper. The 
small group of embryo initials at the tip of the suspensor first develops into a 
“massive meristematic group” of cells, in which the growing points of the 
embryo are organized, much as in Ginkgo, even the “lateral cones” being vis- 
ible as small protuberances in the axils of the cotyledons. The suspensor 
increases in thickness greatly by centrifugal additions from superficial pe 
of the root cap, as in Ephedra. ‘The whole intraseminal development of 
embryo seems to be completed before the seed falls, and covers a period of 
about four months from the time e alewanag A few seeds collected in 
1907 germinated in 1910. mm! 
7 ROSENBERG, ANNA, Ueber ae Poe der Katalase in den Pflanzen. Ber. 
Deutsch. Bot. Gesell. 28: 280-288. 
*8 Pearson, H. H. ie of Welwitschia. Annals of Botany 24:759- 
766. pl. 64. 1910. 
