

xx,v ANTS AND PLANT-STRUCTURE 401 



To this category belong the creeping rhizomes 

 of some ferns which are often beaded with globose 

 swellings inhabited by ants ; e.g. of PhymatodeS 

 Schomburgkii, ]. Sm., a not uncommon fern on shady 

 rocks and trees by the Rio Negro. [In a small Poly- 

 podium, found by Dr. Jameson on the river Napo, 

 the moniliform character of the rhizomes seems to 

 have become permanent, for he did not see a single 

 specimen wanting it ; but the presence of ants in 

 all the swellings revealed the origin of the latter.] 



A curious epiphytal genus of Solanacese, Marckea, 

 whereof I gathered two species on the Rio Negro 

 and Uaupes, is singularly affected by ants. The 

 stem is reduced to a large tuber sometimes as big 

 as a child's head and attains that size through the 

 agency of ants, who inhabit its hollow interior and 

 cover it outwardly with paper of their own manu- 

 facture. From the tuber radiate several branches, 

 simple or sparingly forked. The leaves are very 

 like those of Acnistus arborescens, save that they 

 are verticillate (or at least approximated) in one 

 species (M. ciliata, Benth.) in threes and in the other 

 species in fives; but the large hypocrateriform 

 corollas, with a tube 3 inches long, are more like 

 those of some Gesnerea. There are perforated 

 swellings at the forks of the branches, and some- 

 times also at the leaf-nodes, which serve the ants 

 as detached apartments. I did not see a single 

 plant wanting the basal tuber. 



4. Of Elongated and J^isfn/ose Stews and Branches 



There is an order of plants, whereof several 

 genera and species inhabit Equatorial America, and 

 VOL. ii 2 D 



