30 A. G. Tansley. 
LITERATURE REFERRED TO. 
1. Coulter and Chamberlain. “Morphology of Gymnosperms.’’ Chicago, 
1910, and literature there cited. 
2. Kraus. “ Ueber den Bau der Cycadeenfledern.” Pringsheim’s Jahrbiicher 
IV, 1866. 
3. Le Goc. “ Observations on the Centripetal and Centrifugal Xylems in the 
Petioles of Cycads.” Annals of Botany, XXVIII, 
1914. 
4. Nestler. “ Ein Beitragzur Anatomieder Cycadeenfledern.” Pringsheim’s 
Jahrbiicher XXVII, 1895. 
5. Pavolini. “ La Stangevia paradoxa, Th. Moore.’’ Nuovo Giorn. Bot. Ital. 
XVI, 1909. 
6. Scott. “ Studies in Fossil Botany.’’ London, 1909. 
7. Sinnott. “ Evolution of the Filicinean Leaf-Trace.” Annals of Botany, 
XXV, 1911. 
8. Solms Laubach. “ Die Sprossfolge der Stangevia und der iibrigen Cycadeen.” 
Botan. Zeitung XLVIII, 1890. 
INTERNATIONAL PHYTOGEOGRAPHICAL EXCURSION 
(I.P.E.) IN AMERICA, 1913. 
(i continued from Vol. XII, p. 336). 
The Great Plains Region—Akron, Colorado. 
A KRON is a little town, very typical of the newer “ middle west,” 
lying in the heart of the Great Plains about 100 miles from 
the eastern foothills of the Rocky Mountains. About four miles 
from the town is the experiment station of the United States 
Department of Agriculture—one of the most important of the 
federal agricultural experiment stations, and largely devoted to the 
interests of the dry-farming and stock-raising carried on in this 
district. 
At this station members of the staff of the Bureau of Plant 
Industry of the federal department have for some years been 
carrying on a series of very important large scale experiments on 
the water requirements of plants—particularly of the commonly 
cultivated crop-plants—wheat, alfalfa, sorghum, corn, etc., and of 
the native plants also. An account of the first series of these 
experiments by Drs. Briggs and Shantz has just been published 
(Bulletin 284 of the Bureau of Plant Industry, 1913). In 1911 
