446 MR. G. BENTHAM ON COMPOSIT. 
posed have been usually classed under Helenioidex, on account of 
their scaly pappus ; but their affinity appears to me to be much 
greater with Verbesinex, of which they have the habit, the palea- 
ceous receptacle, &c., so much so that some species of Calea 
where the pappus is occasionally or constantly deficient, are diffi- 
cult to distinguish from Sabazia and its allied Verbesineous genera. 
Of the seven genera composing the subtribe, all well defined, if 
taken in their extended sense, three (Balduina, two species, Mar- 
shallia, three species, and the monotypic Blepharispermum) are ex- 
clusively N. American, three ( Galinsoga, three species, Calea, about 
sixty species, and Tridax, six species) are widely dispersed over the 
tropical and even subtropical regions of America, one species of 
Galinsoga and one of Tridax having become extensively spread as 
introduced weeds, the former in the temperate and tropical regions 
of the Old World, the latter within the tropics only. The 
seventh genus, Dubautia, four species, is insular, limited to the 
Sandwich Islands. 
10. The subtribe Maprex forms a very natural group, con- 
nected, it is true, with the Helenioidez as well as with the Helian- 
thoidew, but most nearly so with the latter, and with a very 
limited geographical range. Five genera (Madia eight species, 
Hemizonia about twenty-five, Lagophylla three, Layia about 
twelve, and Achyrachena one species) belong to western N. 
America from Mexico to British Columbia, one of the species re- 
appearing in Chili. These might all be easily regarded as a 
single genus. The two other genera of the subtribe, differing 
more perhaps in habit and the large size of the capitula than in 
any important structural characters (Wilkesia, one species, and 
Argyroxiphium, two species), are insular, limited to the Sandwich 
Islands. 
6. Helenioidee. 
The essentially American Helenioides connect the American 
Helianthoidese with the Old- World Anthemides on the one hand, 
and with the cosmopolitan Senecionidez on the other. The tribe 
is generally considered as forming three subtribes, or divisions of 
Senecionidez or Helianthoidez ; but it appears to me that the cir- 
cumscription of these large groups is more natural if they are 
kept distinct. The Helenioidee are not numerous in species, but 
varied in form; the species (not quite half as many as those of 
Anthemidex, under one third of those of Helianthoidex) average 
