1&4 BOTANICAL GAZETTE [AUGUST 
which permits two readings to be made with a very short time period between. 
An atmometer cup is mounted over a reservoir from which it may be cut off 
at will by means of a glass cock. It is also connected with a finely graduated 
burette from which the water will be drawn when the reservoir cock is closed. 
A reading can be made in a very short time at any desired intervals, and the 
average evaporating power for the period of observation can be calculated. 
Comparison of different environments is easily made.—CuarLeEs A. SHULL. 
Embryo sac of Oenothera.—IsHikawa” has published a very full account 
of the behavior of the gametophytes and the fertilization phenomena in Oeno- 
thera nutans and O. pycnocarpa, as well as in their hybrids. These two species 
were formerly included in O. biennis. The embryo sac arises from either the 
chalazal or micropylar megaspore, and often both develop simultaneously into 
complete embryo sacs. The sac is tetranucleate, lacking the antipodals and 
one of the polar nuclei. In fertilization one of the male nuclei fuses with the 
remaining polar nucleus, resulting in diploid endosperm. Self-sterility of some 
of the hybrids is due to feeble growth of the pollen tube. Tetranucleate 
embryo sacs occur also in Ludwigia, Gaura, Godetia, and Circaea.—J. M. 
Iron in nutrient solutions.—Corson and BAKKE,” working upon wheat and 
Canada field peas, have studied the relative merits of ferrous and ferric phos- 
phates in nutrient solution. They find that iron in the nutrient solution is 
more important than generally considered; that ferric phosphate is more 
effective than ferrous phosphate, especially for wheat; and that ferric phosphate 
in the concentration senso by SHIvE (0.0044 grams per liter) gives maxi- 
mum dry weight.—Wm. CROCKER 
Polyembryony.—Harvey,® in connection with recording a case of poly- 
embryony in Quercus alba, has given a summary of the recorded cases of poly- 
embryony in angiosperms. The list includes 36 cases, scattered through “15 
of the 49 alliances.” In the case of Quercus reported two vigorous embryos 
occurred in the acorn, and it is of special interest because this is said to be the 
first reported case of polyembryony “‘in the first 13 alliances of the Archi- 
chlamydeae.”—J. M. C. 
© IsHIKAWA, M., Studies on the embryo sac and fertilization in Oenothera. Ann. 
Botany 32:277-317. pl. 7. figs. 14. 1918. 
7 Corson, G. E., and Baxxe, A. L., The use of iron in nutrient solution for plants. 
Proc. Iowa Acad. Sci. 24:477-482. 1917. 
%® Harvey, LeRoy H., Polyembryony in Quercus alba. Mich. Acad. Sci. Rep. 
1917. 3290-331. 
