396 NOTES OF A BOTANIST CHAP. 



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while to do more than indicate some of the species. 

 The solitary instance known to me in Chrysobalans 

 is that of Hirtella 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 alse 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 length 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 Amaiona 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 Reniijia physophora, 

 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 



