244 abstracts: botany 



return and dark, are described, in part by the aid of photographs 

 obtained by rotating cameras, and are in a measure explained. The 

 question as to whether the hghtning discharge is direct or alternating 

 is discussed and reasons offered for believing it to be usually if not 

 always direct. 



In addition to the above such subjects as the spectrum of lightning, 

 duration of discharge, length of streak, chemical effects and danger; 

 cause of thunder, distance heard, rumbling, etc., are all briefly dis- 

 cussed. W. J. H. 



BOTANY. — A text-hook of grasses. A. S. Hitchcock. The Macmillan 

 Co. Pp. 1-276. September, 1914. 



The work consists of two parts, the first being devoted to economic 

 agrostology, the second to systematic agrostology. Part I includes 

 an elementary account of such subjects as pastures, meadows, lawns, 

 reclaiming sand-dunes, and the grass-crop areas. Part II is devoted 

 to morphology and taxonomy, with a chapter on ecology and another 

 on nomenclature. 



The morphology of the vegetative and floral organs is discussed in 

 considerable detail. The classification adopted is essentially that of 

 Hackel in Engler and Prantl's Pflanzenfamilien. Although this ar- 

 rangement, especially of the tribes, is in some respects unsatisfactory 

 and artificial, it is, according to the author, the best system yet pro- 

 posed. There is a key to the 13 tribes and, under each tribe, keys 

 to the genera found in the United States. Paragraphs are devoted 

 to those genera that include economic species, and the more impor- 

 tant of these are described and illustrated. Special paragraphs are 

 devoted to such subjects as the origin and classification of the wheats, 

 the cultivated varieties of sorghum, and the weedy species of Bromus. 



Appended to Part I is a list of government publications referring 

 to forage crops and special uses of grasses; and to Part II a list of 

 books and articles relating to taxonomic agrostology. 



A. S. H. 



