TAXONOMY OR CLASSIFICATION 155 



ulated above the glumes; spikelets usually laterally 

 compressed. 



There are exceptions to all these characters. In some 

 cases the exceptional genera are clearly related to others 

 that conform to the above definitions. Other genera are 

 more or less anomalous and are tentatively placed in the 

 category to which they seem most nearly related. In 

 Isachne the lower floret is perfect and similar to the 

 upper, but it is evidently allied to Panicum and hence is 

 placed near that genus in the first series. Several genera, 

 such as SphenophoHs, Spartina and Alopecurus, have an 

 articulation below the spikelet so that the latter falls 

 from the pedicel, in which respect they agree with the 

 first series, but in most characters they agree with the 

 second series, in which they are placed. In Phalarideae 

 of Series II the imperfect florets are below the terminal 

 perfect one. 



196. The tribes of grasses. — There are 6 tribes in the 

 first series and 7 in the second. The following key to 

 these tribes is not made to cover exceptional genera, since 

 to do this for the sake of a comparatively few genera 

 would make the keys unnecessarily complex. 



Series I 



A. Spikelets round or dorsaUy compressed; hilnrn 



short. 



B. Lemmas and palea very thin and hyaline, 



the glumes much thicker. 



c. Inflorescences monoecious, the staminate 



and pistillate flowers in different parts 



of the same plant Tribe 1. Mayde^b 



cc. Inflorescences not monoecious, usually a (Chap. 15). 



mixture of perfect and staminate or 



neutral spikelets Tribe 2. Andropogone^ 



BB. Lemmas and paleas membranaceous or (Chap. 16). 



thicker, not thin and hyaline. 

 c. Lemmas thinner than the glumes. 



