RHODOSPERME &. 127 
which the tetraspores are placed. Tubercles (on other individuals of the 
species), which are produced on short stalks, fringe the stems and midribs, 
and contain the spores. Old stems which have not been disturbed during 
winter put forth a new crop of leaves as the spring advances, and I have 
always observed that the colour of these biennial specimens is always 
more brilliant than that of plants of the first season. This species is found 
in tolerable abundance all round the British coasts ; itis met with on most 
of the Atlantic shores of Europe, and in several situations in the southern 
hemisphere. It is easily displayed on paper, and is deservedly a universal 
favourite. Delesseria sinuosa, represented at Fig. 115, commonly known 
as the ‘*‘ Oak-leaf Delesseria,’’ is extremely variable in the size and form of 
its leaves. Some are long, narrow, and sinuated, jagged or cleft from the 
margin to the midrib; while others are broad and hardly cleft at all, being 
very slightly sinuated or indentated, such specimens bearing a very striking 
resemblance to young oak leaves. Its place of growth is on the stems of 
the deep water Laminaria digitata (Fig. 46), portions of which are often 
cast ashore with splendid bunches of this Delesseria attached to them. 
In this species the midrib is very distinct, and in full grown plants is 
strong and wiry, presenting occasionally no small difficulty in mounting 
the specimen in a natural position. Each lobed portion of these oak-like 
leaves is traversed by a prominent vein, which arises on each side of the 
midrib and terminates only with the margin of the leafy membrane. These 
veins in the leaves of the Delesseriw, are nothing more than a closer 
aggregation of deep-coloured cells; but the mid-ribs, although composed 
entirely of cellular matter, thicken and harden into a wiry, stick-like sub- 
stance, and become the stems from which subsequent branches and leaves 
are produced. The colour is a deep brownish red, turning to a greenish 
yellow in decay. Spore-bearing tubercles are produced in the midribs; 
tetraspores are placed in little slender marginal leaflets, which are some- 
times so abundant, that the leaves of such specimens appear as though they 
_were fringed with cilia. This species is biennial, and is abundant on the 
Devonshire coasts, being particularly fine in Torbay and in the neigh- 
bourhood of Plymouth. D. alata is the most common species of this genus. 
It grows in rock pools under the shade of the Fuci, or kelpweeds. and on the 
stems of Laminaria digitata (Fig. 46). The fronds vary in length from 3in. 
to 10in. or more. They are much branched, and all are furnished on each 
side of the midrib with a winglike membrane, which is entire at its margin, 
and varies in width from one line to jin. In mounting luxuriant specimens 
of this plant, it is very desirable to cut away superabundant branches ; 
otherwise the delicate membrane on each side of them cannot be effectively 
displayed ; neither can the beautiful transverse striz with which its surface 
is marked be made out under the lens, unless the branches are separated 
from each other. Spores are contained in spherical tubercles produced 
from the midrib; tetraspores are placed in leaflets which arise from 
the angles of the upper branches, or sometimes on each side of the midrib 
in the tips of the terminal branches. Fig. 116, represents a branch of D. 
