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394 NOTES OF A BOTANIST CHAP.
of this species that the plants grow sometimes where
they are totally overwhelmed by the periodical floods,
rendering them a precarious dwelling-place for the
ants. This leads to the suspicion that some of the
sacciferous species, growing far away in the forest,
may have sprung originally from T. planifolia,
which grows on the river- banks ; and even that
some of the epiphyscous, anaphyscous, and hypophyscous
species may be mere varieties of one
another, or may have had a common progenitor
at no very remote epoch. This and many other
interesting problems can only be solved when
naturalists shall become permanent members of the
fauna of Equatorial America, and not as now have Jo
be classed among "occasional visitants"; for their
solution would require observations to be carried on
through many consecutive years on the same spot.
Besides Tococa, there are other allied genera of
Melastomes, viz. Myrmidone, Mart., Majeta, Aubl.,
and Calophysa, DC., which have sac-bearing leaves
infested by ants. They are all found in the forests
of humble sparse growth called "caatingas," and
especially where the soil of white sand, or the
granite floor almost bare of herbs, lies low and is
liable to get transformed into a shallow lake in the
time of heavy rains, thus driving ants and other
insects to take refuge in the trees and bushes. Of
Myrmidone I gathered four species, including the
original M. macrospenna of Martins. They are
low-growing, sparingly-branched shrubs of 3 to
S teet ; the leaves of each pair are very unequal
in size, the smaller one sometimes even obsolete,
the larger saccate, as in the Tococa Anapkysctf,
but the sac always rugose as well as unisulcate ;