Untitled - The Alfred Russel Wallace Website

ANTS AND PLANT-STRUCTURE 403
calyces, is common all along the Amazon, both on
the river banks and in marshy inland sites ; and
solitary trees of it are often seen standing
out above
the Cacao plantations. T. Schomburgkii, Benth., a
smaller tree, grows in the same way on the Upper
Orinoco and Casiquiari. These trees, as well as
the other arborescent Polygonese, have slender
elongated tubular branches, often geniculate.at the
leaf-nodes, and nearly always with perforations, like
pinholes, just within the stipule of each leaf, which
are the sallyports of the garrison, whose sentinels
are besides always pacing up and down the main
trunk, as the incautious traveller finds to his cost
when, invited by the smoothness of the bark, he
ventures to lean his back against a Tachi tree.
I suspect that the remote progenitors of these
ants have at first sheltered in the ocrea (sheathing
stipule) which is so characteristic a feature of the
; Polygoneae but, having found the wood soft and
thin and the pith easy to scoop. out, have made
their more secure abode within the stem and
branches.
Some Tachi trees seem as if they were actually
trying to run away from the ever-encroaching ants.
Coccoloba parimensis, Benth., found by Schomburgk
in British Guayana and by myself on the river
Uaupes, is an arbuscle with a stem 15 teet long,
that tapers upwards and arches over so as finally
to touch the ground, the ants all the while hollow-
ing it out, as it
hopeless attempt
stretches away apparently in the
to escape their invasion. Some
slender Coccolobas climb high into the adjacent
trees, not by twining but by crooking their branches
and thereby hoisting themselves up ;
others
arc