tuca of A g a r d h (and I have specimens from himself), is quite
another plant, and agrees much better with the descriptions of
D i l l e n i u s and L in n æ u s . It adheres most closely to the
paper upon which it is dried, and acquires a fine shining surface.
Ulva latissima 0Î L in n æ u s and A g a r d h , on the contrary,
scarcely adheres at all to the paper, and has, comparatively
speaking, a dull surface. Its size is vastly larger, its colour
darker, and its substance thicker.
Having resided during the spring of the present year (1827)
on the sea-coast, 1 availed myself of the opportunity to study
the progress of several Algæ, from their early to their mature
state. From what I observed in regard to the present species,
I am induced to suspect that there is no natural separation between
the Agardhian genera Tetraspora and Ulva, the only
alleged decided difference being a tubular and a plane frond.
Ulva lactuca has unquestionably a tubular obovate frond, till
lacerated by the action of the waves. From observations made
by my friend Mr H a s e l l upon Ulva latissima (specimens of
which I have seen in his collection), I believe that it also is of
a similar form in its young state.
A g a k d h has quoted under this species the Ulva lactuca
of L i g h t f o o t ; but it appears to me exceedingly doubtful
whether that botanist knew the plant. I f he did, he also has
confounded it with U. latissima, since he gives it an extent of
growth from two inches to a foot or more in length ; and at the
same time seems uncertain what the U. latissima really is.
Fig. 1. Ulva lactuca, natural size. Fig. 2. PoHim o f the frond, magnified.