396 iNOTES OF A BOTANIST 
while to do more than indicate some of the species. 
The soHtary instance known to me in Chrysobalans 
is that of Hij'tella physophora, Mart, a slender 
arbuscle growing just within reach of inundations 
in the forests about the mouth of the Rio Negro. 
The distichous, oblong, apiculate leaves are nearly 
a foot long, and at the cordate base have a pair 
of compresso-globose sacs tenanted by ants. On 
cutting open the sacs I was rather surprised to find 
them lined with cuticular tissue and hairs, just like 
the underside of the leaf ; which seems to show 
that they have been produced by a recurvation of 
the alae of the leaf, through the ants nestling at 
first (Aphis-like) under the leaf and causing it to 
become bullate, and that the recurved margins have 
at leno^th reached and coalesced with the midrib so 
as to form a pair of sacs. 
Rubiads afford a few instances of sac-bearing 
leaves, especially in the genus Amaiona (Aubl.). 
In caatingas of the Rio Negro, almost throughout 
its extent, grows A^naiona saccifera, Mart., a small 
bushy tree with leaves three together, above a foot 
long, obovate with a minute apiculus, tapering to 
the base, where there are two contiguous sacs in- 
habited by small red fire-ants. The fruit resembles 
a large plum (except that like the leaves it is 
harshly hairy), and when ripe is soft and edible ; 
but long before it reaches that stage the ants crowd 
on it and seem to suck the juices through the pores 
of the cuticle. 
To the same order belongs Reviijia physopkora, 
Bth., a remarkable tree found at the falls of the 
Uaupes, having the aspect of an Amaiona, but the 
dry capsules and other characters of Cinchona and 
