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 as- 
signed 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 dif- 
ferent view and look upon Pouzolzia as a sub-genus, 
the following species can, as such, be easily incor- 
porated 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 exa- 
mined, several very distinctive features, applicable to 
the division of the species into groups, well fitted to 
facilitate their discrimination. But for these, in a ge- 
nus 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 
(saltem inferiora) opposita ;” and 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, Ilook 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- 
ticelled leaves appertain, to the second, all the alter- 
nate 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 fea- 
tures, whieh show that they are truly natural, and 
might, perhaps with justice, be separated as distinct 
gous, but not certainly because the fruit of the 
tter are “sulcatus nec alatus" for, with the excep- 
tion of P. cymosa, (probably a true Parietaria), they 
nearly all either produce 4 wings or show a ten- 
dency in that direction, by being 4-angled through the 
thickening of four of the veins which may be assumed 
either to be the costæ of 4 cohering sepals, or ihe 
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 Thoumu- 
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 imper- 
fect 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 numer- 
ous 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 ground- 
less. They principally appertain to those having 
wingless fruit and verticelled leaves, my more extend- 
ed 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 their 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 happens, 
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 part of one fully deve- 
loped, for in full-grown specimens it is occasionally 
found that male flowers have, at the extremities, al- 
most 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 determin- 
ation 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 anti- 
cipated, 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 be- 
lieve 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, how- 
ever, is a point which remains to be ascertained. 
p») 
