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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 Polypodium,
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
the presence of ants in
specimen wanting it ; but
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 sometimes
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