INTRODUCTION. vii 



" A Empty glumes three to six at the 



base of each spikelet." 

 " A A Empty glumes two." 



" X Plants strictly dioecious," etc. 

 " XX Plants hermaphrodite," etc. 

 " n Flowering glumes cordate 



at the base." 



" D D Flowering glumes not 

 cordate at the base. . . . 

 AA. etc." (referring to the 

 next series of divisions in 

 the key). 

 "AA. Spikelets closely imbricate, arranged in a 



linear, dense false spike" 

 "BB. Spikelets densely imbricate, crowded in short 



spikes" etc. 



" CC. Spikelets in small fascicles which are united 

 in a glomerate or interrupted panicle." 

 " aa. Panicles one-sided. . . 252. Dactylis." 



Our analysis by the key has thus brought us to the 

 genus Dactylis, No. 252, and on page 161 we find given 

 further characters belonging to it. We learn here also 

 that the genus contains but one species, Dactylis glomer- 

 ata L. or Orchard-grass, its geographical distribution, 

 that it is "a first-class fodder-grass, especially for heavy, 

 wet soils," that it is very productive, growing rapidly 

 after cutting, and endures shade. There is also a figure, 

 illustrating the inflorescence and a single spikelet, on 

 page 102. 



Orchard-grass was selected to illustrate the use of 

 the keys not only because it is widely distributed, either 

 naturally or in cultivation for hay, and therefore readity 

 obtainable, but also because its analysis required such 

 an extended use of the key. There are very many 

 genera requiring much less reading in their analysis and 

 possible of determination far more quickly. The man- 

 ner of procedure is practically the same in every case. 

 While the keys are in the majority of cases a certain 

 guide in determining the genus, the statement made on 



