HOW TO USE THE KEYS 



To learn the specific name of any grass listed in this 

 bulletin — with a specimen of the mature grass, having the 

 flowering panicle, in hand — turn 



1. To the "Key of the Tribes" of grasses just after the 

 general description of the "Gramineae," The Grass 

 Family. There you will find sets of descriptions of 

 various characters arranged in pairs of co-ordinate 

 rank, followed by other co-ordinate pairs but 

 subordinate to the lirst pair, each in an increasing 

 order of subordination. Under the first pair of 

 coordinates will appear all its subordinates of all degrees 

 of subordination, and the second pair of coordinates 

 may be recognized as beginning the same distance from 

 the margin as the first. Each of these sets of charac- 

 teristics is in the nature of a question which the student 

 must ask himself, and the answer is always yes to one 

 question and no to the other of the coordinate pair; but 

 which is "yes" must be decided from an examination of 

 the specimen. Thus in the first key either the "Spike- 

 lets fall from the pedicels entire," etc., or the "Spike- 

 lets have the rachillae jointed above the empty glumes" 

 and these glumes remain after the "seeds" have fallen. 

 Suppose the first of these two conditions is correct for 

 the grass in hand ; then the grass must belond to Tribes 

 I. II, III or V. Then one must decide the next question 

 in order: are the "Flowering glumes hyaline" (i. e. 

 thin and transparent) or are those of the perfect flower 

 "similar in texture to the empty glumes or thicker," 

 etc. Suppose the answer to the first question is yes, the 

 grass must belong to Tribes I or V. Then are the 

 "Spikelets in pairs" or "not in pairs"? If the former, the 

 grass is in Tribe I, Andropogoneae. Then turn 



