and certain Indian Terebinthacee. 359 
If the attempt is to be at present made, the most obvious 
ground which could be immediately proposed, is that which was 
rejected by Willdenow ; the presence and form of the nectary or 
disk encompassing the ovary. In many species of Amyris it is, 
as a nectary or glandular ring, wanting; being only shadowed 
or represented by a fleshy receptacle or continuous podogynium 
elevating the germ and receiving the filaments and petals in- 
serted in its foot. In other instances the nectary is clearly pre- 
sent, consisting in a glandular ring, which girds the base of the 
germ, distinct from the receptacle beneath it, in which the sta- 
mina and petals are inserted. It is discriminated from that by 
a difference of form and appearance, or more simply separated 
by a contraction or intermediate strangulation. In some in- 
stances the annular receptacle of the germ or nectarial ring is 
crenulate; in others it is MEER glandular; in a few it is 
merely protuberant. 
The total absence of a nectary, and consequent restriction of 
the common receptacle of stamina and petals below and germ 
above to a simple podogynium, might serve to characterize one 
group in this family. Many species of Amyris belong to it: 
among them may be enumerated several Indian sorts, as 4. nana, 
A. acuminata, and A. pentaphylla of Roxburgh. 
À crenulate ring occurs in Bursera serrata; and this form of 
the nectary intimates analogy with Boswellia, which has a crenu- 
late fleshy cup, in the exterior margin whereof the stamina are 
inserted. "That analogy is strengthened by the examination of the 
seed, which exhibits in both instances multilobed and intricately 
folded cotyledons. ‘the presence of a crenulate nectary, there- 
fore, might be taken for the discriminative mark of one more 
group,—a link in the chain from the first-mentioned towards 
Boswellia. | 
Intermediately occurs another, in which the nectary is present 
OL. XV. 3A but 
