430 PROCEEDINGS OF THE AMERICAN ACADEMY. 
blunt or bristle-tipped, as well as hairs truly capillary or setiform or 
awn-like, simple, barbellate, or plumose, rarely clavate or even gland- 
tipped, all occur within the tribe. 
With rare exceptions it has been found possible to distinguish pretty 
readily between the truly capillary pappus of such genera as Lupa- 
torium, Mikania, or Brickellia and the also terete but stiffer bristle- 
formed pappus characteristic of Agrianthus and of certain species to be 
segregated from Ageratum. On the other hand it is believed that this 
bristle-formed pappus can in practically all cases be distinguished from 
the scale-pappus of the true Ageratums and that it forms a useful 
basis of separation for some elements long classified with Ageratum. 
More difficult is the sharp distinction of plumose pappus from forms 
in which the setae are merely barbellate, and while this traditional 
character seems almost necessary at times it has been employed as 
sparingly as possible. 
A distinction which is more important and which seems never to 
have been adequately studied even by close students of the Compositae 
is the difference between a very short cup-shaped, saucer-shaped, or 
coroniform pappus, such as occurs in Ageratum § Coclestina, and the 
similar low and often slightly angulate or toothed annulus which often 
‘erowns the mature achene in genera like Alomia, which lack all true 
appus. When seen on fully ripe achenes from which the corolla has 
fallen away these structures often’ appear considerably alike, yet 
even in this late stage differences are usually to be noted. The. 
true pappus, even when very rudimentary, inclines to be cup-shaped 
and possesses a thin edge. The annulus is a mere low usually thickish 
cartilagineous or fleshy ring with a blunt edge. If examined in a 
younger stage, while the corolla is still in place, it will be seen that the 
true pappus, however rudimentary, is distinctly exterior to the base 
‘of the corolla, while the annulus is merely the ringlike base from which 
the mature corolla disarticulates. This base sometimes enlarges 
slightly after the corolla falls and has in such species as Ageratum 
echioides or more properly Alomia echioides been taken for a true and 
much reduced pappus. In the peculiar genus Jaliscoa the annulus 
takes on a saucer shape and has frayed quasi ciliolate edge, yet when 
carefully examined in a young state it can be seen to be a sub-corollar 
rather than an extra-corollar structure. ; 
To add to the complexity an intra-corollar disk is often present 
various rudimentary forms, as for instance in minute fleshy or glandu- 
Jar papillae or in a fleshy ovoid, depressed-globose, or napiform en- 
largement at the base of the style, capable of some persistence the 
mature achene. 
