248 BOTANICAL GAZETTE [MARCH 
which no phosphate or lime was used. Good field methods along with labora- 
tory methods are necessary for answering such questions. 
McLean finds that middle aged leaves of the coconut absorb carbon 
dioxide faster than either immature or old leaves. These leaves also show a 
maximum i morning, a depression at midday, a second rise in the after- 
noon, followed by the final decline at sunset. Detached coconut leaves showed 
about the same rate of absorption as attached ones, but the maxima occurred 
at different times of day. Sugar-cane leaves absorb much more rapidly than 
coconut.—WM. CROCKER. 
Nitrites and nitrates in plants——Strownp3’ has worked on the relative 
accuracy of various methods for determining nitrites and nitrates in plant 
tissues. He finds that both the Devarda and Schloesing methods with proper 
modifications give fair accuracy. Various other methods tried proved unsatis- 
factory. StTRowp% also finds strong evidence that the reason for failure of 
nodule production (in soy bean) in the presence of nitrates is due at least in 
part to the effect of the high concentration of nitrate in the sap upon the growth 
and reproduction of Rhizobium leguminosarum. He finds that the amount of 
sugar present decreased with an increase in nitrates, but that some sugar was 
always present. It is unknown to what extent shortage of sugar is significant. 
The concentration of nitrates in the roots is far in excess of the concentration 
in the soil bathing the roots.—Wm. CROCKER. 
Humidity and irrigation.—In the Imperial Valley, California, the irrigation 
of 400,000 acres of arid lands is commonly supposed to have been accompanied 
by a decided increase in atmospheric humidity. That this is not the case is 
shown by data collected by McGrecor,” who concludes that no appreciable 
influence is exerted upon atmospheric humidity by the amount of irrigation 
water used, seasonal fluctuations in humidity being accounted for through 
factors of much greater geographical extent.—Gero. D. FULLER. 
Conifer grafting.—The case of a natural grafting of spruce upon pine is 
reported by RoMELL,* who has also investigated the nature of the union as 
seen in the structure of the wood cells. Along the line of contact there was 
found evidence of the character of the pits of each being influenced by the 
proximity of the tissues of the other.—Gero. D. FULLER. 
37Strowp, W. H., By determination of nitrites and nitrates in plant tissue. 
Soil 7 10: 333-342. 192 
———, The is as nitrates to nodule production. Soil Science 10:343-359. 
1920. 
39 McGrecor, E. A., The relation of irrigation to humidity in a recently reclaimed 
desert. Plant World 22:45-52. figs. 3. 19109. 
R Lars-Gunnar, Anatomy % a crabiiae of spruce on pine. Meddel. 
Fran Statens Skogsférs. 16:61-66. figs. 2. : 
