YALUE OF CHARACTERS. 363 
globular and echinulate in the remaining tribes ; but several excep- 
tional genera or species have already been noted, which, if they 
had been confined to genera otherwise anomalous, such as Stokesia, 
might have tended to establish the value of the character. But 
Steetz has also separated, on this character alone, plants which are, 
on every other account, evidently congeners ; and it remains to be 
observed whether some of the differences noted may not be indi- 
vidual only or even dependent on age or degree of development. 
The presence or absence of staminodia, or abortive or imperfect 
stamens in the female florets, has been regarded as a character of 
some importance; and it is, in a few cases, perhaps generic, but 
never much to be relied on. These staminodia are frequently to 
be met with, and perhaps constant in some genera, in Mutisiacee, 
in Petrobiee, and a few other Helianthoides, and a very few 
Senecionideæ, rare, if ever observed, in Asteroides, Inuloideze 
(except one or two species of Buphthalmex), Helenioidez, and 
Anthemide:e. 
6. Differences in the Corolla. 
The corolla of Composite is superior and gamopetalous, with a 
valvate estivation throughout the order with as much uniformity 
as has been observed in the essential characters of the andreecium 
and pistil. It is usually pentamerous, but not unfrequently 
tetramerous, and occasionally trimerous—differences which are 
sometimes generic, frequently specific or sexual only, or variable in 
the same species, never tribual. The available differences consist 
in the varied development of the limb, whether regular or irregular. 
The first and most obvious distinction which strikes the eye of 
the most careless observer is that between the tubular and 
the ligulate limb, giving three principal forms of flower-heads— 
the discoid (where the corollas of all the florets are tubular), the 
radiate (where the external ones are ligulate and the central ones 
tubular),and the liguliform (where all the corollas areligulate). But 
on further investigation this distribution requires to be modified. 
The ligulate corollas of the Cichoriacez do not correspond to those 
of the ray in other tribes. In the Cichoriacez, or true Liguliflorz, 
the ligula is 5-merous; it consists of the whole of the five united 
petals forming a flattened lamina, truncate and shortly 5-toothed 
at the end (Plate VIII. fig. 1), and this with the utmost uniformity 
throughout the tribe; whilst in all other Composite, collectively 
distinguished by Weddell and others as Tubuliflore, when the 
