268 WILLIAM H. LAMB 



ond flower. In other genera of this tribe, as Agrostis (Red Top), 

 this rachilla is wanting. 



The Aveneae have come as a side line from the Festuceae by 

 a modification of the position of the awn. In the Festuceae 

 the awn when present is always terminal, but in the Aveneae 

 it is always dorsal. 



By a modification of the inflorescence another side line 3 has 

 arisen from the Festuceae which has produced two tribes, the 

 Hordeae and the Chlorideae. The Hordeae, which include such 

 grasses as wheat, barley and rye, were produced by a shortening 

 up of the panicle or the raceme of the Festuceae into a spike — 

 the spikelets being sessile in two rows, one on each side of the 

 main stem or rachis. The Chlorideae have come from the 

 Hordeae by further modification of the inflorescence. In this 

 tribe the sessile spikelets are arranged in two rows, but both 

 rows are on the same side of the rachis, giving the spike the 

 appearance of having a single row of spikelets. 



THE PHALARIDEAN LINE 



The Phalaridean Line, characterized by having spikelets with 

 larger flowers at the top, has produced the Phalarideae, the 

 Paniceae, and the Oryzeae. The Phalarideae are distinct in 

 that the spikelet, which is jointed above the empty glumes or 

 scales, has only one perfect flower which is contained in the 

 fifth glume or scale. The four empty glumes are to be regarded 

 as vestiges of flowers which have been eliminated in the reduc- 

 tion of the spikelet. 



The Paniceae have arisen by a direct line from the Phalarideae 

 by a reduction of the spikelet. A joint is found below the empty 

 glumes instead of above as in the Phalarideae. As representa- 

 tive of the Paniceae the millets are probably best known. 



The Oryzeae have been produced as a side line from the Phala- 

 rideae by a lateral flattening of the spikelet, which contains 



3 A tribe that has arisen as a side line is one that has been produced by modifi- 

 cations of minor importance. It is, therefore, very closely related to the parent 

 tribe and may very properly be regarded as a sub-tribe. 



