2S0 
MR DAVID DON 
fructification, is very variable, and, therefore, as a charac- 
ter, is of Httle importance in this order ; but the regularity 
and constancy in the increase of the number of these parts 
is truly admirable, and affords a fine and satisfactory illus- 
tration of the correctness of Mr Brown's beautiful theory, 
regarding the increase in number of the parts of fructifica- 
tion, and the proportions which they bear to each other. 
In some genera, for instance, Pleroma and Melastoma, 
where we sometimes find the calyx of six divisions, the pe^ 
tals are constantly six, and the capsule has always six cells, 
The stamens regularly double that number ; and, there- 
fore, for every additional part, two stamens are always 
added. Aublet, in describing his Blakea quinquenervis, 
has evidently mistaken the exterior scales for the calyx, 
and confounded the true calyx with the capsule. The 
same botanist states, but very incorrectly, that the anthers 
of Melastoma burst lengthwise into two cells. Although 
the Topohoea of Aublet recedes somewhat from Blakea, in 
its being parasitical; yet, notwithstanding, in the Lamber- 
tian Herbarium are several unpublished species, from Don 
Jose Pavon, natives of Peru, and not parasitical, which 
agree with Topohoea in every essential point; and these, 
also, accord well with Blahea, except in having four, 
instead of six scales, surrounding the calyx, which, how- 
ever, is a variable character ; and, therefore, I think myself 
justified in uniting these two genera. Some may, probably, 
think the differential characters I have given too diffuse ; 
but, in an order like this, where so intimate an affinity exists 
among the individuals which compose it, we are obhged, 
for the sake of perspicuity, to introduce, perhaps, characters 
of minor importance. 
