356 BOTANICAL GAZETTE [april 



above 2800 m.; mosses are common about springs up to 3600 m., but liver- 

 worts are entirely lacking. More than one-half the species (210) are classed 

 as belonging to the central Andes, 60 being endemic. There are no endemic 

 genera, but notable among this group are such aggregates as 6 species of 

 Adesmia, 2 of Boopis, 12 of Senecio, and 2 new varieties of Koeleria. The 

 other elements are the northern tropical with 16 species, the subtropical with 

 21 species, the basal Argentinian with 56 species, the southern Andean with 

 10 species, the Patagonian with 73 species, and the cosmopolitan and intro- 

 duced species numbering respectively 28 and 17, This introduced element 

 must be regarded as small when it is recalled that the Mendoza River valley 

 has been the trans-Andean route for centuries. 



Photographs and careful drawings of many of the interesting forms add 



much to the value of the report. — Geo. D. Fuller. 



Crop centers. 



cology 



recently been rendered by Waller, 1 * who has illustrated by w r ell chosen 

 examples the close relation that exists between crop and vegetation centers. 

 Transeau has shown how closely vegetation centers are indicated by a map 

 showing the ratio of rainfall to evaporation, and Waller now emphasizes the 



similar 



It 



r 7 — — i *-J mf 



is often said that crops are moving west or north, which merely means for 

 the most part that we are finding their range. For example, wheat was 

 first cultivated away from its proper center, so that in the last 70 years the 

 center of wheat cultivation has moved 700 miles west and 100 miles north. 

 A fundamental difference between crops and native plants is that when the 

 latter extend far beyond their range, it is chiefly in the poorest soil, since 

 competition with plants proper to the district exclude them elsewhere. Crops 

 grown at the edge of their range, however, must be grown in the best condi- 

 tions available, and of course are exempt from competition. Special atten- 

 tion is paid to corn, wheat, and cotton, and the maps showing their distribu- 

 tion are very significant. Of course there are many complexities in working 



out the thesis. 



ms 



transportation, figure very largely. Considering its origin, the center of corn 

 might be sought south; competition with cotton is thought to be the major 

 factor here. The dominance of eastern Illinois in corn production, and of 

 North Dakota in the production of spring wheat, are related to edaphic fac- 

 tors; in each case there is rich prairie soil.— H. C. CoWLES. 



Increasing catalase activity in yeast cells,— Euler and Blix 14 have deter- 

 mined the effect of various conditions and reagents upon the catalase activity 



* Waller, A. E., Crop centers of the United States. Jour. Amer. Soc. Agron. 

 10:49-83. Jigs. 8. 1918. 



« Euler, H. V., and Bldc, R., Verstarkung der Katalasewirkung in Hefezellen. 

 Hoppe-Seyler Zeit. Physiol. Chem. 105:83-114. 1919. 



