514 BOTANICAL GAZETTE [DECEMBER 
more irregular. The character of these cells is also very similar to that in 
the cycads, where the sheath cells right and left of the centripetal xylem are 
similarly pitted. It is very different from that described by Dr. Stopes for 
C. principalis. She states that the sheath of this form is composed of two 
parts, an inner of long and slender elements and an outer of short and large 
ones, both with bordered pits.33 Recently Miss Benson has described a 
form (C. Felicis), from the Lower Coal measures of England, with a much 
less definitely differentiated inner sheath. LicNnreR considers that the “bois 
diaphragmatique” which he has described corresponds to this “inner sheath” 
in both these forms. If this conclusion is correct, and there seems little doubt 
that it is, then his form and that of Miss BENSON have less specialized and more 
cycadean sheaths than that of C. principalis. The bundles of these two forms 
would thus stand nearer to the Poroxylon type, of the detailed structure of 
which Scort in his Studies in fossil botany (p. 508) says it is “‘in fact, that of a 
cycad.” It is interesting to note, in passing, that JEFFREY has chosen the spe- 
cialized principalis type for comparison with Prepinus and the Abietineae, 
while the other is in substantial agreement with the araucarian leaf bundle. 
Licnrer describes at some length the differentiation of certain glandular 
cells within the bundle sheath. The scelerenchymatous strands above and 
below the bundle differentiate early, and the mesophyll as well. The cells 
of the latter have an abundant “protoplasme chlorophyllien probablement 
accompagné d’hydrates de carbone.” The palisade consists ultimately of two 
or three layers of cells. The epidermis was very poorly preserved and afforded 
no new data. The bundles were seen to dichotomize, as in ordinary cordaitean 
leaves, though Licnter says that the division does not occur in the same way as 
Stopes has described in the case of C. principalis. 
The type of leaf Licnter has described is very similar to that of the living 
broad-leaved forms of the Araucarineae—R. B. THoMson. 

Water requirement of plants.—Briccs and SHantz3s have conducted a 
series of experiments upon the water requirements of certain crop plants an 
obtained results which are important not only in determining the most econom- 
ical plants to cultivate in semi-arid regions, but also in indicating a profitable 
line of purely ecological research with the natural vegetation of various habitats. 
The term “water requirement” indicates the ratio of the weight of water 
absorbed by a plant during its growth to the dry matter produced. € 
exhaustive review of the literature of the subject will be of great service ” all 
interested in this and allied problems, and demonstrates the fact that while a 
considerable number of experiments have been performed by a number of 
33 New Phytol. 2: pl. 9. fig. 6. 1903. 34 Ann. Botany 26: 201-207. 1912. 
3s BricGs, L. J., and Saantz, H. L., The water requirements of plants. I. wit 
tigations in the great plains in 1910 and rogrt. . A review of the literature. ©» 
Dept. Agric., Bur. Plant Ind. Bulls. 284 and 285. pp. 49 and 96. 1913. 

