394 NOTES OF A BOTANIST 
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 hypo- 
physcous 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 to 
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. niacrosperma of Martius. They are 
low-growing, sparingly-branched shrubs of 3 to 
8 feet ; the leaves of each pair are very unequal 
in size, the smaller one sometimes even obsolete, 
the larger saccate, as in the Tococa AnaphysccE, 
but the sac always rugose as well as unisulcate ; 
