64 BOTANICAL GAZETTE [JANUARY 
(the ravine). On the steppe, Sanguisorba officinalis transpired more rapidly 
than Clematis integrifolia, 3.3 gm. against 1.2 gm. In the ravine the reverse 
was true, 1.7 gm. against o.7 gm. Similar results were found for Phlomis 
pungens and Ajuei Laxmanni, with the former transpiring more rapidly in 
the steppe and less rapidly in the ravine. These facts are explained hy the 
rapid closure of the stomates of Sanguisorba and Ajuga in the exposed position, 
and the slow closure in the other forms. In another experiment, two marked 
xerophytes, Aster villosa and Veronica incana, showed much higher transpira- 
tion than two evident mesophytes, Aristolochia clematitis and Sanguisorba 
officinalis. The losses in these forms were respectively 43.3, 15, 11.3, and 
6.4 gm. These results are explained by the stomates being closed in the 
mesophytes and open in the xerophytes. 
It was rather a common thing to find higher transpiration in a given meso- 
phyte in the ravine than on the steppe, owing to the stomatal closure in the 
latter place. In Ajuga Laxmanni, there were 10.5 gm. on the steppe against 
26.2 in the ravine; in Centaurea orientalis, 17.6 gm. against 31.5 gm. 
nan riment with Helianthus annuus, Pisum sativum, Vicia Faba, and 
Panis fagopyrum placed in a series of positions where the evaporation 
power of the air graded from a low value to a high, the transpiration rose with 
the evaporation power of the air up to a certain height, then it fell enormously 
with the rise of the evaporation power of the air. The break was the point 
at which stomatal closure was induced. When the author started with various 
mesophytes and xerophytes, all with the stomates open, and placed them in 
. conditions where the evaporation power of the air was rather high and rising 
rapidly, as time elapsed the mesophytes showed rapid transpiration, rising 
rapidly with the evaporation power of the air for two hours or so, followed by 
a rapid fall. In this case there is a high and sharp pointed curve. The xero- 
phytes showed slower initial transpiration, a far slighter rise with the evapo- 
ration power of the air, and no such marked fall. In this case, the curve 
is flat, with no very high or sharp point. Itjrn believes the two types of 
curves represent mesophytism on the one hand and adaptation for xerophytism 
on the other. The xerophyte can protect itself against excessive transpiration 
in exposed positions without curtailing extremely the CO, necessary for carbon 
assimilation by rapid or extreme stomatal closure. This work indicates the 
great importance of stomatal variation in regulating transpiration, especially 
in mesophytes, a conclusion quite in contrast with that of LLoyp.—WILLIAM 
ROCKER 
Alpine plant-geography.—RvDBERG," in the first three of a series of articles 
on the phytogeography of the Rocky Mountain region, has discussed the 
alpine zone, its environmental conditions, geographic floristics, and plant 
76 RyDBERG, P. A. » Phytogeographical notes on the Rocky Mountain region. }- 
Alpine region; II. in of the alpine flora; III. Formations in the alpine zone. 
Bull. Torr. Bot. Club 40:677-686. 1913; 41:89-103, 459-474. 1914. 
