DISTRIBUTION OF TRIBES. 453 
the reduction of the female corollas. This approach to Cotules is 
thus traceable both in geographical distribution and in structure. 
Tanacetum, about thirty species as we now propose to limit it, 
belongs exclusively to the northern hemisphere; for the South- 
African species retained by Harvey in the genus appear to be 
much better placed in Schistostephium. It has been found diffi- 
cult to draw up definite structural characters constantly to 
distinguish Tanacetum from Chrysanthemum ; for the most impor- 
tant difference, the female florets, short and tubular or filiform in 
Tanacetum, ligulate in Chrysanthemum, is unavailable in the few 
species or varieties where the female florets are deficient; and 
therefore Schultz Bipontinus and some others have brought a 
large number of the common Chrysanthema into Tanacetum. But 
this appears to me to-be a very unnatural combination ; and in the 
few cases which might otherwise have been doubtful, habit comes 
in aid of the distinction. Tanacetum also, on the other hand, runs 
as much into Artemisia; and in order to maintain some order in 
the tribe we must here, as in Asteroidez, admit as genera large 
and prominent groups, although they may be confluent on their 
borders. 
Tanacetum has a more Eastern range than Chrysanthemum; 
there are but few in Europe or in the West-Mediterranean region, 
more numerous in the Levant and Central Asia; some species 
extend into the far north, and thence into North America, where, 
in the mountains of the western regions, are two endemic species 
with some slight structural peculiarities which induced Nuttall to 
propose them as a distinct genus, Spheromeria. 
Artemisia, to which some botanists ascribe near 200 species, 
with the same general centre as Tanacetum, Asiatic rather more 
than European, has a wider range. Abundant in the temperate 
regions of the northern hemisphere throughout the Old World, 
it has also many Alpine and Arctic species, and spreads not only 
over the greater part of North America, but also down the 
western ranges of mountains to extratropical South America. 
Geographically Artemisia thus meets there with the genus Ambrosia, 
possessing a somewhat similar foliage, nodding capitula, a style in 
some respects similar, and, according to Delpino, a similar anemo- 
philous fertilization, to which characters I have already alluded 
under Ambrosiez ; but here the affinity ceases. There is nothing 
in Artemisia of that perfect separation of the sexes, of that free- 
dom or very slight connexion of the anthers, of their peculiar 
