YALUE OF CHARACTERS. 857 
very few striking exceptions to the normal form, although perhaps 
specific only. 
Of the further modifications of the pappus, there is one upon 
which great stress is often laid, as being of supposed absolute 
generic importance—the difference between the simply setose 
(where the setz are denticulate or scabrous only) and the plu- 
mose (where the sete are bordered by fine cilia like the plumes 
of a feather). But the value of this character has been much 
overrated. The plumose pappus occurs most frequently in 
Cichoriaceee, Mutisiace:, and Cynaroidez; in the two former tribes 
it is often constant in otherwise good genera ; in Cynaroideee it is 
also not uncommon, but rarely accompanied by other marked 
differences ; it is little more than a specific character in Onopordon, 
Jurinea, Tricholepis, Centaurea, dic. ; and if we have maintained it 
for the technical separation of Cnicus from Carduus, it is partly 
from convenience, on account of the large number of species it 
separates—partly on geographical grounds; for the American 
species, which are now numerous and pass into a distinct type 
in other respects, have always the pappus plumose. In the other 
tribes the plumose pappus is rare, occasionally constant in small 
but natural genera, in other instances passing gradually through 
allied species into the simply setose. The difference is indeed 
but one of degree; the lateral denticulations or cilia are always 
the same in relative position. When they are shorter than the 
diameter of the pappus-ray or main seta, the latter is termed 
simply scabrous or denticulate, when they shortly exceed that 
diameter it is said to be barbellate, and plumose only when they 
are considerably longer. The intermediate barbellate stage, how- 
ever, is much more rare than the simply denticulate or the 
decidedly plumose state. 
Another distinction often of some importance, and much insisted 
upon of late, especially by Weddell, is, in those very frequent 
cases where the setose pappus parts with its achene— whether it 
falls off altogether, the setee being united in a ring at the base, or 
whether each seta falls off separately. This character is often of 
much avail in several genera of Cichoriacee ; and Weddell made 
use of it chiefly in aid of the difficult discrimination of some 
Gnaphalioid genera or subgenera, and at first sight very success- 
fully; but a closer investigation of a much larger number of 
species than he had at his command has in some measure lowered 
again the "— value of the character. 
