OBSERVATIONS ON THE COMPOSIT. 43 
received by botanists of the last century, and which are so 
treated by so prominent a systematist as M. Baillon. With 
these plants before us we stand, therefore, face to face with 
one of the most difficult problems in systematic botany. 
There is no agreement at all among the most critical of 
investigators as to how the limits of a genus in Composite shall 
be determined. The supreme value of that general make-up 
which we call habit may be satisfactorily trusted in one 
instance, but not in another, it would seem. The form of the 
involucre, and the number and imbrication of its bracts, are 
found decisive with some authors but are rejected by others. 
The form of the achene and the nature of the pappus are 
relied upon by one man and wholly distrusted by another. 
If a question be raised as to what ought to be received as the 
proper circumscription of Eupatorium, it becomes difficult 
to decide to what author of genera appeal should first be made. 
To attempt to start with Linneus’ Genera Plantarum is futile. 
It is not likely that a botanist lives, or ever did, who, by the 
sole help of the Linnean diagnosis of Hupatoriwm, could 
decide what manner of plants should compose this genus. 
His assertions that the achenes are “oblong,” and that the 
pappus is “plumose,” would exclude all the species known to 
him, and all that any authors thus far have referred to it. 
This kind of fact will commend itself to the reflection of 
those who have recently proposed that the publication of a 
genus shall depend upon a verbal diagnosis only, and with 
Linneous as the initial author. The only way which the 
botanist has or ever had of learning what this author means 
for Eupatorium, is the way of laying aside the “Genera” 
and taking up the “Species,” in which latter he finds light; 
though not from any specific description or diagnosis, but 
only by seizing upon the bibliography given, and going back 
to older authors who had given figures or descriptions or 
both. In his diagnosis, the one phrase which gives at least 
a hint of the genus, is that relating to the style, which is 
described as “very long,” with “branches straight and erect;” 
