488 MR. G. BENTHAM ON COMPOSITAE. 
Upon the whole it would appear from the above Tables that 
Composite are not unfairly distributed between the New and the 
Old World as well as to numbers as to variety of forms, 
although with a balance in both respects rather in favour of 
America, the numbers being 4525 species in 421 genera in the 
New World, against 4920 species in 387 genera in the Old. 
Further discoveries may also, probably, inerease this disparity ; for 
there are many tracts in the great mountain-chain extending from 
California to Chili, so rich in Composite over the whole of its vast 
extent, which are as yet but little known or wholly unexplored, 
whilst in the two richest Composite regions in the Old World, 
the Mediterrrnean and South- African, the Composite forms as yet 
unknown must be comparatively few. From tropical Africa we 
may expect rather more, especially as to generic forms ; but these 
may be compensated by fresh discoveries from the interior of 
Brazil and La Plata. Were the insular floras included in the 
enumeration, the disparity would again be slightly diminished ; 
for the imperfectly known Mascarene and the well-explored 
Atlantie Islands would add 18 genera and species to the Old 
World, whilst the Sandwich and Galapago Islands, now pretty 
fairly investigated, only add 8 genera and 70 species to the New. 
St. Helena, New Zealand, and the South-Sea Islands are wholly 
excluded from these caleulations, as not being specially referable 
to either of the two great divisions. 
With regard to the comparative diversity and distinctness of 
forms in the two divisions, it may be observed that the number of 
species to a genus is about 107 in America, and 1277 in the Old 
World, showing in the former more numerous remnants of old 
types, in the latter a greater luxuriance of flourishing and in- 
creasing genera. It will be seen, however, that in each division 
there are regions remarkably characterized in both respects. 
‘When we come to consider the tribes into which Composite 
have been divided, we at once see a great disparity in their repar- 
tition between the two great divisions. Two tribes are almost en- 
tirely American, the Eupatoriacee and Helenioidez. In the former 
30 genera, including above 200 species, are exclusively American, 
3 genera, containing together above 80 species, have each one of 
their species extending into the Old World. Eupatorium itself, of 
above 400 American species, is represented in the Old World by 
about 10 species; and the small genus Adenostyles alone has an Old- 
World preponderance, having 2 European and 1 Californian 
