ABSTRACTS 



Authors of scientific papers are requested to see that abstracts, preferably pre- 

 pared and signed by themselves, are forwarded promptly to the editors. The 

 abstracts should conform in length and general style to those appearing in this issue. 



BOTANY. — The influence of cold in stimulating the groivth of plants. F. V. 

 CoviLLU. Journ. Agr. Res. 20: 151-160. Pis. 20-35. 1920. 



The dormancy of trees and shrubs begins before the advent of cold weather. 

 Cold weather is not necessary to bring about dormancy. It is necessary to 

 bring about renewed growth in the spring. If not subjected to cold, dormant 

 plants will not start growth in the spring. Even on the same plant a branch 

 which has been chilled will start growth under proper conditions while an 

 adjoining branch which has not been subjected to chilling will remain dor- 

 mant. The best temperature for chilling is 32° to 40° F. It may be applied 

 in either light or darkness. 



During chilling the reserve food stored in the form of starch is changed to 

 sugar. Until this change has taken place the plant is unable to use the 

 stored food for renewed growth. H. V. Harlan. 



BOTANY. — Revisions of North American grasses. A. S. Hitchcock and 



Agnes Chase. Contr. U. S. Nat. Herb. 22: 1-77. Pis. 1-24, figs. 



1-20. 1920. 



This number of the Contributions consists of four independent papers: 



(1) The North American species of Ichnanthus, by Hitchcock; (2) The 



North American Species of Lasiacis, by Hitchcock; (3) The North American 



Species of Brachiaria, by Chase; (4) The North American Species of Cen- 



chrus, by Chase. Ichnanthus is a tropical genus allied to Panicum. Lasiacis 



is a tropical genus of woody grasses, also allied to Panicum, one species of 



which extends into southern Florida. Of the 6 American species oi Brachiaria 



two extend into Texas. The species of Cenchrus are usually known as 



sandburs. Eight of the 13 species described are found in the United States. 



A. S. H. 



BOTANY. — Revisions of North American grasses. A. S. Hitchcock. 

 Contr. U. S. Nat. Herb. 22: 115-208. Pis. 25-32, figs. 21-62. 1920. 



This number of the Contributions includes four independent papers on the 

 North American species of the genera Isachne, Oplismenus, Echinochloa, 

 and Chaetochloa. Isachne and Oplismemis are tropical genera, one species 

 of the latter extending into our southern states. The species of Echinochloa 

 are widely distributed, some of them being common weeds. One of the forms 

 of E. crusgalli, barnyard grass, is cultivated under the name of Japanese 

 barnyard millet. The species of Chaetochloa (Setaria) are also widely dis- 

 tributed. Some species are common weeds, such as C. lutescens, yellow fox- 

 tail, and C. viridis, green foxtail. One species, C. italica, is the commonly 

 cultivated millet, or foxtail millet, one form of which is called Hungarian 

 grass. One species is grown in greenhouses as an ornamental, the broad 

 plaited blades giving it the name of palm grass. Twenty-six species are de- 

 scribed and figured. A. S. H. 



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