immersed in tlie midrib, towards the tips of the branches, very convex.
Tetraspo7'es either contained in terminal sori, disposed at each side oi tlie
rib ; or else in proper leaflets, irregularly grouped about the apices. Colour^
in well grown specimens, a clear, deep crimson, varying to dark full red,
and sometimes brownish. Substance membranaceous, adhering to paper.
The cells of the frond are small and close, for the genus.
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One of our commonest species ; and though not without
beauty, yet one of the least attractive of the genus to which it
belongs. When well grown, with a broad wing to the stems, as
in the specimen selected for our upper figure, its claims to the
possession of considerable beauty and grace will readily be admitted,
but in average specimens the wing-like margin is much
more narrow and is very liable to injury ; the colour darker and
more dingy; and the ramification less regularly dichotomous.
Sometimes, from proliferous growth, the whole upper part of the
frond is thick and bushy.
Under PL LXXXIII. of the first volume will be found a statement
of my views respecting the claims of D. angustissima to
specific rank,— claims, which I did not then admit, and which I am
not now disposed to do. That supposed species I can only regard
as a very narrow and aberrant form of the present plant, having
either no membrane developed, or a very imperfect one. Were
it true that no membrane was ever found in L . angustissima,
then we should have an absolute character on which to found a
species. But such is not the case, for I have specimens in which
the commencement of membrane is evident on some of the
branches, while other parts, equally perfect, are destitute of
membrane. I consider L . angustissima therefore to be an
extreme variety of B. alata, analogous to the narrow states of
such plants as Cliondrus crispus.
Fig. 1. D e l e s s e e i a a l a t a ; A broad variety. 3. Narrow variety:— both
the nat. size. 3. Apex of brancb witb tetraspores. 4. Apex with the same,
contained in proper leaflets. 5. A tetraspore. 6. Apex witb tubercles.
7. Section of a tubercle. 8. Portion of the lamina and midrib :—magnified.