82 BRITISH -MARINE ALGAE. 
extremely beautiful. The joints of the stem and branches are a fine olive 
green, and are distinctly marked, while the two-parted capsular fruit- 
vessel is of a reddish-brown, and is surrounded by a hyaline or transparent 
border, forming a pretty contrast to the olive green stem and branches 
of the plant. A fruited sprig is represented at c (Fig. 80). E. fenestratus, 
(d) so called from the peculiar lattice-like markings on the surface of the 
silicules, is a small and not very attractive species. I have taken it at 
Plymouth and Whitsand Bay. The tufts are about 3in. high, the fila- 
ments are very thread-like and sparingly branched, the ramuli few, 
distant, and usually alternate along the branches. The silicules, or fruit- 
vessels, when present, are abundant, and are stalked, being produced at 
irregular intervals on each side of the branches. These silicules are of a 
larger size than the fruit-vessels of any other species of Ectocarpus, and 
may be known at once by their shape, which is elliptical, but rather 
narrow at each end, and by the peculiar transverse and cross markings 
all over their surface, a character which has suggested the specific name 
of this plant. A portion of the stem, bearing two silicules, is represented 
at d. EH. Mertensii (e), dedicated to Professor Mertens, of Bremen, is one 
of the most charming of its tribe. It was discovered at Yarmouth, in 1779, 
and, although it is widely distributed, it is generally considered a rare 
species. I have had fine specimens sent to me from Peterhead and other 
northern stations, but the plants taken by me at Plymouth exceed in 
size and beauty every other specimen I have seen hitherto. This beautiful 
plant is in perfection in May and June. It is found on muddy rocks at 
low-water mark. The main stems are from 5in. to about 10in. long; the 
branches are numerous, and are of unequal length, being set throughout 
with lesser branches, all of which are branched on the same principle, and 
every division of branches and branchlets is invariably opposite, a re- 
gularity of growth which gives to the plant a beautiful feathery appear- 
ance. The whole plant is abundantly furnished with short pointed ramuli, 
which are placed opposite to each other at very short distances, usually at 
the upper shoulder of every third joint, and it is about the centre of 
these ramuli that the large binate sporiferous mass is produced. The 
jointing of this species is beautifully distinct, as may be seen at e (Fig. 80), 
where also the two-parted spore-vessel is represented. The colour is a fine 
olive green, the substance is flaccid, and, like all these summer annuals, 
this plant adheres closely to paper in drying. Once only have I found this 
rare species in fruit, and that occurred among the specimens I received 
from Peterhead. This fruited plant was so small and poor in appearance 
that I discarded it from my collection; but taking it up subsequently, and 
observing something peculiar on one of its stunted branches, I submitted it 
to the microscope, and found to my great surprise, that my little scrubby 
despised plant was a treasure indeed, being abundantly in fruit. This was 
a lesson to me, which I here record for the benefit of young students, 
never to throw aside any mounted plant, however apparently insignificant, 
until it has been thoroughly examined under the microscope. 
