428 BOTANICAL GAZETTE [DECEMBER 
The periods of shade are denoted on the graphs by a broad black 
line below. 
The graphs show merely a general and qualitative agreement 
between the rates of water loss from the various objects. It is 
quite evident that the white cup fails to show nearly as great fluctua- 
tions with light and shade as do the plants. On the other hand, 
the brown and black atmometers agree fairly well with each other 
‘TABLE I 
LOssES PER 30 MINS., GRAMS OR CC. 
PERIOD EXPOSURE 
Physal. Xanth. Brn. atm. | Blk. atm. | Wht. atm. 
eee Open Pe 3-4 2.9 3-7 2.0 
ee te Open 3.0 4.2 4.3 4.7 2.8 
Sse Canvas shade “7 2.4 4.2 3-4: 2.4 
£05 Canvas shade 1.7 2.4 2.1 2.9 2.4 
See Open 2.7 3-9 3-5 3.8 a 
S..8; Open g. 4.5 4.0 5.0 et 
aR Cheesecloth shade 3.0 3.2 2 4.0 hd 
By, Cheesecloth shade 1.9 4.7 2.5 3-7 2-3 
he Open 4.3 at ei 4.8 3-4 
eee Open Ce 4.2 am 5-3 3-5 
and with the plants. The Physalis plant lost an inordinate amount 
in period 6, the brown cup lost what appears as too much in period 3, 
and the behavior of the Xanthium plant in the last three periods 
is unusual; otherwise the agreement in the different ordinates is 
about what should be expected. Attention may be called to the 
general ascent of the series of three maxima for two of the instru- 
ments, showing clearly the gradual increase of the sun’s intensity 
from 8:00 A.M. to 1:00 P.M. Also, with the thinner shade neither 
of the plants and neither of the dark instruments exhibit such a fall 
in rate of water loss as they do in the denser shade. We may now 
turn to the quantitative relations shown by these series of data. 
Since the use of two different shades really constitutes soles 
separate tests, we may consider the observations for the first six 
periods as test I, and those for the last six as test II, there being 
a common period of sunshine for the two tests. If now we calculate 
the ratios of the two sun periods, respectively, in each test, t© 
those of the shade period intervening, we shall obtain quantitative 
