364 MR. G. BENTHAM ON COMPOSIT X. 
florets of the circumference, or, in a few cases, all or nearly all 
are ligulate, the ligula is trimerous only, consisting of three only 
of the united petals, the two inner ones being reduced to minute 
teeth, or, more generally, entirely deficient (fig. 7). The only 
instances among Tubuliflore of an approach to the Cichoriaceous 
corolla are in Stokesia, a monotypic genus of Vernoniacer, where 
the corollas are irregularly expanded into a 5-lobed lamina, and 
in a very few Mutisiacee and two or three species of Cynaroide:e, 
where the lamina is 4-merous, or even, in a few species, 5-merous, 
almost as equally so as in Cichoriacee. In Cichoriacex, there- 
fore, the corolla gives us an absolute tribual character, but no 
generic ones within the tribe, beyond a few indications derived 
from size or colour. It is the diversity in the corolla of Tubuli- 
flore alone that we have further to consider. 
The corollas of the female florets always differ from the herma- 
phrodite ones of the same species, sometimes only in being more 
slender, very frequently in the shape of the limb; and, in so far as 
the difference is owing to sex alone, the characters to be derived 
from the presence or absence and relative number and position of 
these diverging forms have been already considered under the 
head of sexual differences; but there are other diversities of form 
to which some importance is attached. The most remarkable is 
the so-called bilabiate form of most Mutisiacesz, which had induced 
many to class that tribe as a distinct suborder, under the name of 
Labiatiflore. In that tribe there is in the same head, or in dif- 
ferent species or genera, a gradual passage from the regular 5-lobed 
to the ligulate limb :—first, a slight irregularity, owing to the inner- 
most lobe being more deeply separated than the others; then two 
of the inner ones are more deeply separated or more erect than the 
three outer ones (Plate VIII. fig. 5); then, again, the two inner 
ones shorten, whilst the three outer lengthen and become gradu- 
ally consolidated into a ligula; sometimes the two inner and three 
outer ones are respectively united, the former into a short inner 
lip, the latter into a longer outer one (ñg. 6), or the inner lobes 
disappear altogether, leaving the truly ligulate trimerous female 
corolla of ordinary radiate heads (fig. 7). All these forms are to 
be met with in Mutisiacez, which can therefore no longer be 
absolutely characterized by their corollas. In tbe subtribe Goch- 
natiee, for instance, they are all tubuliform, and as regular as in 
any discoid genus or tribe; and although the well-developed 
bilabiate form is almost limited to Mutisiacew, yet there are a 
