320 BOTANICAL GAZETTE [APRIL 
543.3 and 377.3 per cent, respectively. Expressed in another way, 
the non-aqueous materials of the leaves made up for Physalis 12 
per cent of the whole in the morning and 15 per cent in the after- 
noon, while for Martynia these quantities were 16 and 21 per cent, 
respectively. It thus became clear that there had occurred a 
marked fall in the relative moisture content of these leaves during 
the period from 6 A.M. to 2 P.M., which is what our a-priori considera- 
tions had led us to expect, and our problem seemed to be answered 
in the affirmative. 3 
We present, in the four following tables, the data derived from a 
number of other tests, carried out by a method quite similar to that 
followed in the two tests just described. Besides the two plants 
named above, we dealt with Nicotiana glauca Graham (a woody 
perennial attaining the proportions of a tree), Euphorbia hetero- 
phylla L., Trianthema Portulacastrum L. (a fleshy plant resembling 
Portulaca oleracea L. of the east), Tribulus terrestris L., Sida 
angustifolia Lam., Amarantus Palmeri Wats., Maclura pomifera 
(Raf.) Schneider, Covillea glutinosa, and Prosopis velutina Wooton. 
The two last-named plants are characterized by thin, hard, xero- 
phyllous leaves, the foliage of Covillea (the creosote bush) being 
heavily covered with a shellac-like resinous layer. For the naming 
of our experimental plants we are indebted to the kindness of 
Professor J. J. THORNBER, of the University of Arizona. 
Tables I to IV present the evaporation rates for the periods in 
question, in terms of cc. from the standard porous cup atmometer.” 
The moisture contents of the leaves are given in percentages of 
their dry weight, also the dry weights in percentages of total weight. 
In the first two columns appear periods and evaporation rates per 
hour (cc.) from the porous cup atmometer, these data being quite 
comparable throughout all four series. Evaporation maxima are 
designated by asterisks. In the third column are presented the 
hour at which leaf tests were made. The remainder of each table 
presents the leaf moisture data, each minimum being denoted by an 
asterisk in the second column for each plant, and all the maxima 
by full-faced type. 
* LivIncsTon, “B. E., Operation of the porous cup atmometer. Plant World 
13:111-118. Igio. 
