500 BOTANICAL GAZETTE [JUNE 
an extensive study of diurnal stomatal changes, the influence of physical 
factors on the opening and closing of stomata, and the effects of these stomatal 
movements on transpiration. The main observations were made on alfalfa, 
potato, sugar beet, onions, and cereals, but some sixty species in all have been 
amined. He finds three types of stomatal behavior: the cereal type, typified 
by barley; the thin-leaved mesophyte type, typified by alfalfa; and the 
fleshy-leaved type (not confined however to plants with fleshy leaves), typified 
by such plants as the potato, cow beet, and onion; each of these has a different 
closure reaction to extreme conditions. The cereals show no opening of 
stomata at night, no matter how slight the opening by day has been. The 
thin-leaved mesophytes have the stomata usually open by day and closed at 
night, but under extreme conditions show a closure during the middle of the 
day, correlated with an opening at night. The thick-leaved plants behave 
much as marsh plants do, having their stomata open day and night when 
water content is high and evaporation low, and showing a tendency to close 
only when the evaporating capacity of the air is high. 
Many details regarding the effects of environmental changes, such as light 
intensity, temperature, evaporation, wind flow, water content of soil, leaf 
turgor, and habits of growth on stomatal behavior are presented, from which 
one may draw the general conclusion that stomata are sensitive to environ- 
mental conditions, particularly to light, and to factors that reduce the water 
content of the leaf, and that they open and close as conditions necessitate. 
The evaporation studies indicate that atmometers and potometers do no 
measure accurately the total effect of evaporation factors upon plants, a 
result that is not surprisin 
The final section on the effect of stomatal movement upon transpiration 
by several investigators, including Irjun, who studied the transpiration of 
mesophytes and xerophytes in ravines and on the Russian steppes, and who 
found marked evidences of regulation of transpiration. This work by LorTFIELD 
seems to settle the question definitely in favor of stomatal regulation, particu- 
larly when the apertures are nearly closed. As long as the apertures are more 
than 50 per cent open, the transpirational water loss is controlled by evaporation 
factors alone, but with closure almost complete, the stomata regulate very 
closely the water loss from the plant. The paper is ye emen! illustrated 
with plates showing photomicrographs of stomata.—C. A. SHU 
Anthocyan pigments.—Noacx’ has found rhamnose-free flavonol digluco- 
sides to be much more abundant in green leaves than has generally been 
supposed. In such leaves as he studied he was able to establish the existence 
7 Noack, K., Zeitschr. Botanik 14:1-74. 1922. 
