ON THE [13 



ASCLEPIADE^. 



The vast additions to the number of species which botany 

 is constantly receiving, while they make a natural arrange- 

 ment absolutely necessary to the general botanist, render it 

 at the same time proportionally difficult. For though 

 there are still many tribes of plants easily distinguishable 

 even by a superficial observer, yet there are others, that 

 hitherto have been thought abundantly distinct, which can 

 no longer be circumscribed by means of characters taken 

 from their organs of reproduction. This is perhaps now 

 the case with the Rubiace^ and Apocine* of Jussieu. 

 It is true, that to an experienced observer, it may still be 

 practicable to refer the greater part, perhaps the whole, of 

 these plants to their proper places in a natural series ; tis 

 but it is, I apprehend, no longer so, to distinguish the two 

 orders by definitions derived from the usual source. Such 

 ^at least is the opinion T have been led to form from all that 

 I have seen published respecting them, as well as from 

 what I have lately had an opportunity of observing in New 

 Holland. 



As, however, both these families are already too exten- 

 sive, it becomes expedient rather to attempt their subdivision 

 into smaller groups, which may possibly admit of more ac- 

 curate hmitation, than to unite them into one vast order, 

 the distinguishing characters of which, could they be ob- 

 tained, must probably be extremely vague, and clogged 

 with numerous exceptions. Such a subdivision, it seems 

 to me, may be easily made of the Apocinese, by employing 



