392 MR. G. BENTHAM ON COMPOSITE. 
previously to this dispersion the stock must have existed long 
enough to give absolute permanence and an otherwise unexampled 
constancy to those essential characters of primary importance 
which I shall recur to in detail. The presence of an involucre, 
the symmetry of the floral organs, the abortion of the calyx-limb, 
the estivation of the corolla-lobes, the syngenesy of the anthers, 
and, above all, the structure of the pistil, fruit, and seed are not 
known to offer a single exception throughout the ten thousand 
species of the order. 
But although Composite must thus have existed, in some shape 
or other, but yet with all these essential characters, at an early 
geological period, the differentiation of the larger groups proba- 
bly took place after the isolation of the actual centres of preser- 
vation. Of the thirteen tribes: adopted, two only, Asteroideze 
and Senecionidez, may be said to be cosmopolitan or nearly so. 
Cichoriacew, Cynaroidexe, and Anthemidez belong to the northern 
hemisphere with chief centres in the Mediterranean and Central 
Asiatic regions ; a few, but those (except some Cichoriacez) either 
forming part of or closely allied to Europeo-Asiatic genera, have 
spread over North America and even down the Andes to extra- 
tropical South America. Calendulacee and Arctotides are 
African, extending sparingly into Europe.  Vernoniaces, Eupa- 
toriaceze, Helianthoidee, Helenioidez, and Mutisiaces are essen- 
tially American, but with a few types which may have arisen in 
the tropical and subtropical regions of Africa and Asia. The 
great tribe of Inuloidex is for the most part Old- World, although 
the subtribes Plucheinez and Gnaphaliez have been long enough 
in America to have there formed a very few generic types. Be- 
fore, however, drawing any further. general hypothetical conclu- 
sions as to the early history of the order, and the course of its 
present distribution, it will be necessary to recapitulate succes- 
sively the data hitherto supplied to us by the several tribes, sub- 
tribes, and principal genera it is composed of. For this purpose 
I propose taking the several tribes successively in their systematic 
order, although in the further details under each tribe I shall 
endeavour to take genera and subordinate races as much as 
possible in their natural rather than in their technical limits, I 
shall then proceed to consider the chief centres or regions 
occupied by the present races of Composite, the limits to be 
assigned to them, their distinctive characters and mutual con- 
nexions. I must now, however, observe, to prevent misunderstand- 
