But notwithstanding these variations, showing that
the only character by which the two genera are kept
apart is the linear stigma, I have finally deter-
, mined to adopt the genus, mainly on the ground assigned
by Mr. Bennett, “ well marked peculiarity of
habit and geographical distribution,” as by so doing
I will be enabled to present a comparatively complete
enumeration of its species, which I could not do in
the case of the undivided genus Parietaria, and
should other Botanists feel disposed to take a different
view and look upon Pouzolzia as a sub-genus,
the following species can, as such, be easily incorporated
with the larger group,, ■
The habit, though so well marked that when once
a few species are known, the others are for the most,
part easily recognized, presents, when closely examined,
several very distinctive features, applicable to
the division of the species into groups, well fitted to
facilitate their discrimination. But for these, in a genus
so extensive and upon the whole so natural, their
determination must, in many cases, be very difficult.
Mr. Bennett, in his account of the genus, divides
them into two groups, first, “ Fructus bialatus. Folia
(saltern inferiora) o p p o s ita a n d second, “ Fructus
sulcatus nec alatus. Folia plerumque omnia alterna,”
and even seems to think that they may form the
elements of two distinct genera. A more extended
acquaintance with the genus, shows that they are
scarcely sufficient for the latter purpose, both being
liable to exceptions as shown in plates 1979 and 80.
I have therefore departed from that distribution and
had recourse to the venation of "the leaves, as the
basis of my arrangement which, however, to this
extent only, I look upon as natural.
My first group embraces all those having simply
three-nerved or slightly triple-nerved leaves, that is,
each nerve runs its whole course without conspicuous
branches: the second, those with quintuple-nerved
leaves, that is, those in which the middle nerve or
proper costa gives off, generally near its middle, two
conspicuous lateral branches and the lateral ones
several others, but all on the outer side. To the
first of these nearly all those with opposite and ver-
ticclled leaves appertain, to the second, all the alternate
leaved ones, and a few with opposite leaves,
are referable. There is a third form found in P.
cymosa, but which I consider referable to the second
group in which all the three primary nerves divide
near the base, producing a many-nerved leaf, though
not,in the proper sense of that term. These two
groups are respectively distinguished by other features,
which show that they are truly natural, and
might, perhaps with justice, be separated as distinct
genera, but not certainly because the fruit of the
latter are “ sulcatus nec alatus” for, with the exception
of P . cymosa, (probably a true Parietaria), they
nearly all either produce 4 wings or show a tendency
in that direction, by being 4-angled through the
thickening of four of the veins which may be assumed
either to be the costaj of 4 cohering sepals, or the
lateral nerves of two; the last supposition seems
the more probable as each extends considerably
beyond the wings forming a kind of two-cleft beak,
which is altogether wanting in the other group.
Apart, therefore, from the 5-cleft involucre, they are
more justly referable to Gaudichaud’s genus Tlioumu-
ria than to Pouzolzia. My own impression is that
the two groups are not true congeners, and might with
propriety be respectively raised to the rank of genera.
I am, however, adverse to this proceeding, because I
think the already existing genera of this order are, if
not too numerous, at all events too loosely defined to
be maintained as they now stand, and that, therefore,
were I to add another it might merely be adding to
the already existing confusion, owing to my imperfect
acquaintance with the rest of the order, and in the
meantime all the Indian species can be easily enough
ranged under Mr. Bennett’s character. Of the numerous
real or supposed species, defined in the following
pages, I already begin to entertain doubts of their
all proving permanent, and suspect, that if leisure
permitted me to go over the ground again with the
same attention that I bestowed six months ago, I
should probably find occasion to reduce some of them,
having in the interval obtained additional specimens of
some which may probably, by throwing further light
on such as were then obscure, show that my first
determination was premature. This, however, is now
quite impossible, I can, therefore, only express a
hope that my fears on this account may prove groundless.
They principally appertain to those having
wingless fruit and verticelled leaves, my more extended
acquaintance with plants of this genus having
shown me that some, indeed many of those having
winged fruit, when full grown, have wingless ones in
the lower fascicles, hence the probability that some of
those described as having wingless fruit, may be
merely junior specimens in which perfectly developed
ones may not yet have been produced, and in regard
to the leaves, I have repeatedly, since this paper was
written, found opposite and verticelled leaves on the
same plant, lowering by so much the value of that
character when not well supported by others more
constant. These facts I think it necessary to mention,
to put others on then- guard against placing too much
reliance on those marks of distinction, as well as to
warn collectors to be always careful in selecting their
specimens. For exhibiting the fructification the most
fully developed branches either in whole or in part
should be taken, that is, in case, as often happeus,
the floriferous portion has grown to so great a length
as to make a specimen, having both leaves and fruit
inconveniently large, to be sure always to add to a
smaller and younger branch a p art of one fully developed,
for in full-grown specimens it is occasionally
found that male flowers have, at the extremities, almost
entirely given place to female ones, all of which
are winged while on younger branches of the same
plant they are nearly as universally males, or if fruit
are found they are wingless, and concealed among the
males. A knowledge of this fact may occasionally
save trouble, and remove uncertainty in the determination
of a species.
The number of stamens is also sometimes variable,
but less so than the foliage and forms of the fruit.
In regard to the accompanying figures I fear some
of them will not be found so useful as I at first anticipated,
for owing to want of room they often fail in
conveying a correct idea of the habit, a point on
which native artists are apt to fail, their drawings
being usually deficient in ease, but. so far as correct
outline can compensate for deficiency of grace, I believe'the
accompanying may generally be depended
on. The analyses are true to the specimens from
which the subjects were taken, but as these are so
much alike throughout they may not prove so useful
as might, a priori, have been expected. This, however,
is a point which remains to be ascertained.