OF PLANTS CALLED COMPOSITE. 277
tains several flowers their expansion is generally ascendent, or in the order of the simple spike. In a spike formed by these many-flowered glumae, as that of Triticum and Lolimn, the expansion of the partial 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 commencing below the apex and proceeding in opposite directions. But as the same descendent expansion takes place in a spike formed of single-flowered glumae, 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 with the fact of a great majority of the order having actually this disposition ; but also with that peculiarity in the vascular structure of the inner valve of the perianthium ; which, whether it be considered as indi- cating that this part is formed of two confluent valves, an opinion I have elsewhere 1 advanced, or merely as a trans- position 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 of Dipsacece and the single-flowered involucrum of Composite is so striking, that it cannot appear very paradoxical to con- [97 sider them as both of the same nature.
In Dipsaceae, however, there is no instance of the outer calyx containing more than one flow T er, and the evidence afforded by inflorescence on this subject is not altogether satisfactory.
In Dipsacus it has been long noticed that expansion begins about the middle of the spike, and proceeds in opposite directions from the point of commencement : this order is evidently more analogous to that of the compound than of the simple spike ; there being several instances of spikes manifestly compound, where the same inversion of the upper part exists.
1 In General Kemarks on the Botany of New Holland [vol. I, p. 55].
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