INTRODUCTION. 337 
and sixty genera, we are compelled to derive our characters from 
inflorescence and its rhachis and bracts, from the pappus or abnor- 
ma] development of the rudimentary calyx, from the shape of the 
corolla, from sexual abortions, from appendages to the anthers, 
from the external form or appendages of the style-branches, and 
from very slight variations in the external form of the fruit, many 
of which, in other orders, are scarcely reckoned of more than 
specific value. 
In Linneus’s artificial sexual system the sexual characters were 
necessarily taken as of primary importance, and the Composite, 
forming the chief portion of the class Syngenesia, are divided into 
four orders :— Polygamia «qualis, with all the flowers (or, as it is 
more convenient to call them, the florets) of each head herma- 
phrodite and fertile ; Polygamia superflua, with the floréts of the 
circumference female, those of the disk hermaphrodite, and all 
fertile; Polygamia frustranea, with the florets of the circumference 
barren, those of the disk hermaphrodite and fertile ; and Polygamia 
necessaria, With the florets of the circumference female and fertile, 
those of the disk hermaphrodite but barren. To these Linnzus 
added a fifth order, which, notwithstanding its analogous name 
Polygamia segregata, is not founded on any sexual distinction, but 
on inflorescence only, being characterized by the numerous uni- 
florous heads crowded on a common receptacle. 
Such an arrangement proved, however, to be purely artificial ; 
the strikingly different groups, for instance, of the Hawkweeds' 
and Thistles, are amalgamated with a few others with which they 
have evidently no other connexion than as members of the same 
family, into the first Linnean order; and notwithstanding the 
endeavours of most subsequent synantherologists to maintain as 
much as possible the value originally attached to these sexual 
distinctions, they have felt repeatedly compelled to unite iato 
single or closely allied genera, species which would, on these 
Linnean principles, be distributed over most or all of his 
orders. 
Jussieu and Ventenat, following up the ideas broached by 
Vaillant, considered the Syngenesia polygamia of Linnsus as a 
class, under the name of CowPosrr x, dividing it into three families 
or natural orders—Cichoriacee, Cynarocephale, and Corymbifere,— 
an arrangement which, up to the date of De Candolle's *Prodromus,' 
was generally followed by the latter, as well as by most other 
French botanists—considering, however, the clase as a natural order 
222 
