IV. 
LAMINARIACEfE. — Agarum. 
95 
VII. AGARUM, Bory . 
Frond stipitate, coriaceous, flat, pierced in all parts with roundish holes, and tra- 
versed by a cartilaginous midrib which is a prolongation of the stipes. Fructifica- 
tion , cloudlike patches of spores , imbedded in the thickened surface of some part 
of the perforated expansion. 
A remarkable genus peculiar to the northern parts of the Atlantic and Pacific 
Oceans, on the American and Asiatic shores. The common American species (A. 
Turneri) is well known in the north eastern states as the Sea Colander , a name 
aptly expressive of the perforated frond. The holes in the membrane exist at all 
ages, but increase in size and circularity, as well as in numbers, as the growth 
proceeds. They are at first merely narrow slits, and commence to be formed near 
the midrib, where the active cell-division seems to take place. As in Laminaria, the 
newest portion of the leaf is at the base, where the stipes enters ; and the apex is 
continually worn out and thrown off. The fructification is found on old fronds 
late in the autumn, or early in winter, and forms very dark coloured patches of 
uncertain extent on the pierced membranes. 
1. Agarum Turneri , Post, and Rupr. ; stipes compressed, coriaceous, continued 
as a flattened midrib through the frond ; lamina membranaceous, its nearly circular 
holes with flat margins, and of various sizes intermixed. J. Ay. Sp. Alg. vol. 1 , 
p. 141. Katz. Sp. Alg. p. 580. Fucus Agarum, Turn. Hist. t. 75. FI. Dan. 1 . 1542. 
(Tab. V.) 
TIab. On rocks and stones, &c., from low- water mark to a depth of 5 — 10 fathoms. 
Very abundant on the Eastern Coasts, from Greenland to Cape Cod. North West 
Coast, at least in Russian America, (v. v.) 
Boot much branched, formed of many clasping, dichotomous fibres, interwoven 
together. Stipe from one to four lines wide, and from two inches to a foot in height, 
compressed, coriaceous, becoming flattened and sensibly widened where it meets the 
lamina, through which it is then continued as a midrib. The width of this 
midrib varies much in different specimens of the same age ; in some being scarcely 
wider than the stipe, and in others three or four times that width. Lamina oblong, 
at first elliptical, then becoming ovate, and at length deeply cordate at the base, the 
margin at the same time being changed from nearly flat to be very much waved 
and curled, this portion of the frond continuing to be developed after growth has 
nearly ceased within it. The whole lamina is pierced, at short distances, with 
roundish holes, which commence of small size and gradually widen ; these are 
irregularly mixed together, large and small, in all parts of the leaf, the smaller 
holes being of later formation than the larger. The new growth of membrane 
chiefly takes place where the stipe enters at the base, but also for a considerable time 
near the margin of the lower half of the leaf. The substance of the leaf is membra- 
