so 
PROCEEDINGS OF SOCIETIES. 
tubercles were pretty freely distributed over both surfaces of the pinna, on the mar- 
gins as well as on the flat surfaces; those seen on the margins, being in profile, 
showed a hemispherical outline, the greater part of which projected beyond the 
margin. I have no doubt of these tubercles being the fruit, and that they are to be 
regarded as conceptacles and superficial. I examined pinnae from two other speci¬ 
mens of D. ligulata, which I had in my possession some years, and in both I no¬ 
ticed traces of the same appearance of fruit, but not nearly so distinct as those on my 
first specimen. In these last the capsules and spores appeared to have discharged 
their endochrome, which is, very probable, as this genus is very impatient of fresh 
water, or even exposure to the air, decomposition commencing almost immediately 
after they are removed from the sea. If the mode of fructification is to guide us in 
the arrangement of the genera under orders, I conceive Desmarestia should be re¬ 
moved from the order Sporochnacae to Dictyotacm, as the fructification I have ob¬ 
served in D. ligulata is much more conformable to the latter order than to that of 
the former. I have not as yet perceived any symptom of fruit either on D. acu- 
leata or D. viridis, but the scattered single spores, so very abundant on Mr. Sawer’s 
late important addition to British botany, Desmarestia pinnatinervia, cannot but be 
the fruit of that species. These spores have the same pink colour as those of D. 
ligulata ; but, instead of being in capsules, they appear on every part of the frond, 
like strings of beads or chains. I think it not improbable that young spring plants 
of the two other species, aculeata and viridis, will reward careful examination by a 
discovery of their fructification, and I would recommend search to be made among 
the Byssoid fibres with which the young plants are clothed. 
I take this opportunity to exhibit some specimens of Desmarestia Pinnatinervia, 
for which I am under obligation to Mr. William Sawers, of Londonderry, to whom 
belongs the honour of adding it to the marine botany of our country. Mr. Sawers 
sent specimens of his plant to the meeting of the British Association, at Hull, and to 
most of our best algologists, some of whom pronounced it a mere variety of a Lami¬ 
naria. At length specimens reached Dr. Montague, of the French Institute, who 
recognised it as his D. Pinnitinervia, a description and figure of which he gave 
in the “ Annales des Sciences Naturelles,” for 1842, vol. xviii. As there are 
some differences between the appearances of the Spanish plant, as described by Dr. 
Montague, and those found by Mr. Sawers, I will refer to a free translation which 
I have made of the article in the “ Annales.” 
“Is it truly a Desmarestia? That is a question not easily decided, in the 
absence of any fructification. M. Aghardh is inclined to believe it is to that genus 
we should refer it. This alga requires careful description, because it has a perfect 
resemblance to Laminaria debilis, collected on the coast of Corsica by my friend 
Mr. Solierol. The only differences which I have found, though essential diffe¬ 
rences, and which separate our plant from those with which I have compared it 
are—first, the presence of a well-defined stipe, about four or five millimetres 
long—second, a midrib, which traverses the entire length of the frond, and from 
which nervures issue to the right and left, at the distance of five and ten millimetres 
from one another, forming, with the midrib, angles of about 24 degs. All these 
nervures, though strongly marked, are of the greatest tenuity. The form of the 
frond is obovate, fourteen millimetres long by eight in width at the widest part, 
which is the summit. It has the same delicate tissue as Laminaria debilis. If it 
is a Desmarestia, as all believe it to be, we must consider the frond as formed by 
the fusion of the opposing pinnules, which will represent the nervures.” 
The differences which I find between the Spanish plant as described by Dr. 
Montague, and the specimens of the Irish plant supplied by Mr. Sawers are—The 
Spanish plant is dentated at the margin, obovate, and the widest at the summit. 
Mr. Sawer’s specimens are entire at the margin, very slightly waved, lanceolate, 
and widest about one-fourth of the length of the frond from the base, tapering 
thence towards the summit; the proportions of length and breadth of the two plants, 
are very dissimilar. However, I am inclined to regard them at present as iden¬ 
tical, merely altered by the circumstance of climate. It is singular that, although 
the figure given in the “Annales” exhibits an appearance of dots, Dr. Montague has 
made no mention of chain-like series of spores, such as are contained in the dots in 
Mr. Sawer’s plants. 
