immersed in the midrib, towards the tips of the branches, very convex. 
Tetraspores either contained in terminal sori, disposed at each side of the 
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. 
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 ad- 
mitted, 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. LXX XIII. of the first volume will be found a state- 
ment 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 avery 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 D. angustissima, 
then we should have an adésolute 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 D. angustissima therefore to be an 
extreme variety of D. alata, analogous to the narrow states of 
such plants as Chondrus crispus. 
Fig. 1. Deresser1a aLaTa; <A broad variety. 2. Narrow variety :—doth 
the nat. size. 3. Apex of branch with tetraspores. 4. Apex with the same, 
contained in proper leaflets. 5. A tetraspore. 6. Apex with tubercles. 
7. Section of a tubercle. 8. Portion of the lamina and midrib :—magnified. 
