116 A TEXT-BOOK OF GRASSES 



latter, however, the inflorescence is really branched, 

 shortened branchlets with 2 spikelets being borne in each 

 of the cavities of the axis. Sometimes, as in Tripsacum 

 and Euchlsena (Fig. 11), the axis disarticulates and the 

 1-seeded joints become hard bead-like fruits. The cob of 

 an ear of corn is a greatly thickened axis of inflorescence, 

 the structure of which is discussed in Par. 202. 



The spikes and spike-like racemes of Chloridese and of 

 many Panicese are 1-sided. Here the axis has developed 

 so unsymmetrically that the 2 rows of spikelets have been 

 forced to one side. The axis may appear thin and much 

 flattened as in many species of Paspalum (e. g., P. repens 

 and P. stellatum) or somewhat triangular with a row of 

 spikelets on each of 2 sides, as in crab-grass. 



The name rachis is usually applied to the axis of spikes, 

 and spike-like racemes or panicles, or to the axis of any 

 contracted inflorescence or portion of an inflorescence. 



147. Branching of panicles. The main branches of a 

 panicle are known as the primary branches. Those which 

 arise from these are secondary branches and this name 

 may be applied to branches of the third or higher order. 

 The ultimate branches or branchlets which are the stalks 

 of the individual spikelets are the pedicels and will be 

 considered when the structure of the spikelet is discussed. 

 The primary branches of a panicle often appear to be 

 verticillate or at least more than one from a node. It 

 will be observed however that in many cases there is 1 

 primary branch and that the others are secondary branches 

 developed at the base of a primary branch. If the verticils 

 are composed of primary branches the aggregation is 

 due to the failure of the internodes to elongate. 



If the several branches originating at one node all stand at 

 one side of the main axis and those at the next node stand on the 



