abstracts: plant physiology 119 



in 16 chapters, each treating of one of the major geologic divisions shown 

 on the map. Under each chapter the statements are arranged geo- 

 graphically according to the coordinates, in alphabetic and numerical 

 sequence. Accordingly the geology of any locality where more than 

 one geologic system is represented is distributed thru the various chap- 

 ters in which those systems are discussed. 



The compiler has depended in most cases on the papers quoted to 

 furnish other references to earlier literature. Nevertheless, there are 

 references in the text to 953 separate papers. Each chapter is accom- 

 panied by a small sketch map showing the areal distribution of the 

 rocks described in that chapter as represented on the geologic map. 



G. W. S. 



BOTANY. — The phylogeriy of grasses. William H. Lamb, Forest 

 Service. The Plant World, 15: No. 11. November, 1912. 



This is a discussion of the origin of grasses, the essential differences 

 between the tribes of grasses, and their probable derivation from a 

 common ancestral type. 



The grasses have come from lily-like plants by a reduction in the 

 number of the parts of the flower. Among grasses the direction of 

 evolution has been toward a reduction in the number of flowers in the 

 spikelet. Forms with relatively more flowers in the spikelet are to be 

 regarded as primitive, and forms that have but one flower in the spikelet 

 have developed furtherest from the ancestral type. 



The first grasses were a primitive group, probably very similar to the 

 bamboos as we know them today, and these are the progenitors, directly 

 and indirectly, of all the other tribes. The Bambuseae have given rise 

 to the other tribes by three great lines of development; the Festucean 

 Line, the Phalaridean Line, and the Andropogonean Line. 



A diagrammatic drawing has been made of the spikelet, the inflores- 

 cence, and the flower of one genus to typify each tribe, and a chart has 

 been arranged which shows the relationship of the tribes of grasses, and 

 the structural modifications which have segregated each distinct group. 



W. H. L. 



PLANT PHYSIOLOGY.— r/ie wilting coefficient for plants in alkali 



soils. Thomas H. Kearney. Bureau of Plant Industry, Circular 



109, pp. 17-25. 1913. 



The object of this investigation was to ascertain whether the presence 



of an excess of soluble salts in the soil affects the ability of plants to 



reduce the moisture content to the limit at which plants wilt and are un- 



