366 MR. G. BENTHAM ON COMPOSIT X. 
character to distinguish Cacalia from Senecio, and Nabalus from 
Prenanthes. This, however, only holds good for North-American 
species. 
The constancy of the venation of the corolla-lobes in Composite 
pointed out by Brown has since been frequently alluded to, and is, 
as it were, the natural consequence of the equally constant valvate 
estivation. The chief minor difference observable in venation is 
in the undivided part of the limb, and results from the prominence 
of the central vein alone of each petal, or from the more or less 
conspicuousness of the lateral veins, those of two adjoining petals 
combined into one, or distinct, and all similar to the central vein. 
The latter arrangement is conspicuous, for instance, in the ligule 
of Trichocline, and comes in aid of the generic character. 
7. Differences in the Calyx. 
The calyx in Compositz is so absolutely deprived of its ordinary 
function (the protection of the young flower), so completely 
absorbed in the ovary, or so absolutely rudimentary at the time of 
flowering, that the only available distinctive characters it affords 
result from the varied impress it gives to the external surface of 
the fruit, or from the forms it acquires as a portion of that fruit. 
These characters, therefore, have been considered under the head 
of the fruit, as those of its ribs and pappus. 
8. Differences in the Ultimate Inflorescence and Bracts (the 
Capitulum, its Receptacle, Involucre, and Palee). 
Inflorescence and its bracts are most frequently classed among 
the vegetative organs, and consequently assigned a low grade in 
the scale of generie characters, too low a one, probably, in many 
cases. In Composite, however, where they are called upon to 
take a part as accessories to the reproductive operation, to supply 
in some respects, the place of some of the reproductive class that 
have been disabled by consolidation, they acquire an unwonted 
degree of fixity, and thence of generic value. Thus it is, that the 
diversities in the flower-head or capitulum, its involucre, receptacle, 
and palez, are properly taken account of in the essential character 
of every genus of the order. 
Whatever be the primary inflorescence of Composite (solitary, 
cymose, paniculate, capitate, or any other form), the ultimate rami- 
fication is invariably a capitulum— several flowers (often very many, 
sometimes very few, or a single one) sessile, or nearly so, on a com- 
