84 



FIRST BOOK OF GRASSES 



and pedicel, the perfect spikelet removed. The 

 spikelets are awnless and the marginal nerves of the 

 first glume are winged at the 

 summit. This inflorescence and 

 that of Lepturus (Fig. 28) are so 

 similar in appearance and func- 

 tion, disjointing with the mature 

 seed permanently attached, that 

 the student may wonder why 

 they are placed in tribes so re- 

 mote as the barley grasses and 

 sorghum. The two illustrate 

 what is not seldom shown in 

 nature, that very different struc- 

 tures may arrive at the same 

 function, although the forms 

 from which they are derived were 

 very remote. The inflorescence 

 of Lepturus is a spike, and its 

 „ -- A , • • * r spikelet shows it to be a reduced 



Fig. 77. A, single jomt of ■'^ 



Taceme o{ Rytuix granu- and Specialized relative of Lo- 

 a '^dii^ram'' of mcWs Hum. The iufloresceuce of Mani- 



and pedicels of three g^pig Jg ^ raceme with twO Spike- 

 joints of raceme, spjke- . . t i i i 



lets removed; D, view lets at a jomt, oue pediceled, and 

 tJZ;JZ.i>S: the perfect spikelet not greatly 

 E, raceme; F, reverse different from that of sorghum. 

 ^^^^' We have just observed the 



rachis joint and pedicel lying closely pressed together. 

 In Rytilix (Fig. 77, A) they are adnate (grown to- 

 gether). Examine the diagram of three joints with 



