356 MR. G. BENTHAM ON COMPOSIT. 
three apparent series, when they are organically in a single one ; 
and these, therefore, should be taken chiefly into account in using 
the pappus as a systematic character. The gradually diminishing 
outer rows, so much less constant in their presence, absence, 
shape, or degree of development than the principal row, may be 
analogous only to those extra teeth or appendages of some Mela- 
stomacee, Verbenacez, &c., which have been called epicalyces. 
The occasionally present reduced innermost row (as in some Cen- 
taureas), which, as above mentioned, may be only a modification 
of the epigynous disk, is of scarcely more than specific value. 
The four principal modifications of the pappus which may be 
made available in the tribual characters are:—1, the setose 
pappus, where the ring consists of a number, often indefinite, of 
bristle-like rays, sometimes very slender and hair-like, sometimes 
thicker or flattened and passing into pales; 2, the paleaceous 
pappus, consisting of a usually smaller and often definite number 
of flattened chaff-like or transparent scales; 3, the aristiform 
pappus, where one, two, three, or more of the ribs of the achene 
are produced into rigid awns or teeth; and, 4, the coroniform 
pappus, where the very short pale: are united in a ring or cup. 
These different forms give very useful and general characters 
without being absolute; for in every tribe there are exceptions to 
the normal pappus, besides that the different forms may pass so 
gradually one into the other as to make it difficult to decide to 
wnich class a given pappus should be referred. The pales may 
be very obtuse or produced into a point which may lengthen into 
an awn, whilst the flattened base may gradually shorten or be 
obliterated, or the pales may gradually increase in number and 
diminish in breadth, till they come better under the designation of 
sete, or they may gradually shorten and unite more or less into a 
corona. Generally speaking, the pappus may be said to be setose 
or slightly paleaceous in Vernoniaces, Eupatoriaces, Asteroides, 
and most subtribes of Inuloideæ ; aristiform or truly paleaceous 
in the subtribe Buphthalmee of Inuloide* and in Helianthoides, 
paleaceous in Helenioides, coroniform or none in Anthemidesze, 
setose again in Senecionidew, none in Calendulacese, paleaceous or 
none in Arctotide:e, setose or slightly paleaceous and usually very 
copious in Cynaroideze, setose or paleaceous in Mutisiacee and 
Cichoriacez. In all tribes there are a few genera or species, and 
in Asteroides, Inuloidew, Helianthoidez, and Helenioidese several 
genera without any pappus ; and in almost all tribes there are a 
