96 Mr. Brown's Obf!crvationt on the 



for which I have already attempted to show that certahi parts 

 of the structure of a syngeiiesious floret arc peculiarly well 

 adapted. 



The circumstance, however, is not confmed to Compositse, but 

 exists in an equally remarkable degree in GraminecE. 



I have formerly considered the gluuia, or what Linneus has 

 termed calyx, in this family of plants, as an involucrum. 



In those genera where this gluma or involucrum contains seve- 

 ral flowers their expansion is generally ascendent, or in the order 

 of the simple spike. ]n a spike formed by these many-flowered 

 gluma?, as that of Triliciim and Loliiini, the expansion of the par- 

 tial spikes, with relation to each other, is descendent, or in the 

 order of the compound spike; in most cases, however, with that 

 deviation, which I have already noticed, of the expansion com- 

 mencing below the apex and proceeding in opposite directions. 

 But as the same descendent expansion takes place in a spike 

 formed of single-flowered glumte, it may be inferred that the 

 genuine type or most perfect form of a grass is to have several 

 flowers in its gluma or involucrum : a view not only consistent 

 Avith the fact of a great majority of the order having actually 

 this disposition ; but also with that peculiarity in the vascu- 

 lar structure of the inner valve of the perianthium ; which, whether 

 it be considered as indicating that this part is formed of two con- 

 fluent valves, an opinion I have elsewhere* advanced, or merely 

 as a transposition of vessels in a simple valve, analogous to that 

 in the syngenesious floret, is evidently adapted to the many- 

 flowered spicula, though equally existing in that with a single 

 flower. 



The resemblance between the outer calyx o( Dipsacece and the 

 single-flowered involucrum of Compositte is so striking, that it 



* In General Remarks on the Botany of New Holland. 



cannot 



