33 



simpler woods growth rings do not become a fixed or structural 

 feature. The simpler type of growth ring occurs in both the 

 Mesozoic and recent cycads, and Chamberlain finds rings in a 

 monocotyl. Accentuation of growth ring must at first have 

 gone on very slowly as measured by geologic periods, and is 

 mainly correlated with the more marked tracheid and wood ray 

 differentiation of mid to later Mesozoic time. — G. R. Wieland. 



BOOK REVIEWS 



Chase's First Book of Grasses* 



The increasing disposition among beginning students in 

 botany to select the grasses as a special field of study will no 

 longer be hampered by the lack of an adequate hand-book. 

 Mrs. Chase has demonstrated, contrary to the practice of the 

 ordinary "How To Know" botanical literature, that scientific 

 method need not be sacrificed in order to make the subject 

 attractive to the beginner. From the beginning she urges the 

 student to study the grasses themselves; but as these cannot be 

 provided in a book, a series of careful drawings, purposedly 

 somewhat diagrammatic, is furnished. The student is made 

 clearly to understand that the classification of grasses is based 

 on the spikelet, and the first lessons are therefore devoted to a 

 careful study of the general structure of the theoretical spikelet. 

 From this generalized spikelet the author passes to a study of 

 its actual modifications in the order of increasing complexity. 

 Beginning with the pedicelled spikelet having more than one 

 floret as approximating most closely to the ideal diagrammatic 

 form, we pass from the simplest type as shown in Bromiis 

 through the best-known typical genera of the tribe Festuceae to 

 the most complex modification of the type in Scleropogon. The 

 returning to the simple spikelet illustrated in Brcrmis, a fresh 

 start is made along another line of differentiation, which leads 

 us from the simplest type of sessile spikelet in a two-sided spike 

 as shown in Agropyron through the various modifications of 

 spicate inflorescence to its greatest complexity in Hordeum. 

 The progressive development of the spikelet with more than 



* Chase, Agnes. A First Book of Grasses. Pp. 121, 94 figs. New York> 

 The Macmillan Co. 1922. $1.00. 



