08 LAMINARIACE^—Choeda. iv. 



1. Chorda filum^ Stack. ; frond cartilaginous, lubricous, clotlied with pellucid 

 hairs, filiform, very long, tapering to each extremity, not constricted at the dissepi- 

 ments. Grev. Alg. Brit. t. 7. Harv. PJiyc. Brit. t. 107. Kiltz. Sp. Alg. p. 548. 

 Scytosiplwn filum, Ag. — /. Ag. Sp. Alg. 1, p. 126. 



Hab. On rocks, etc. in the sea, between tide-marks, and extending to 4 — 10 

 fathoms depth, especially in deep, quiet bays. Common on the northern shores, (v. v.) 



Root a minute disc. Fronds from one to ten, twenty, or even forty feet in length, 

 according to depth of water, scarcely twice as thick as hog's-bristle at the base, 

 gradually increasing in thickness to the middle and there from a quarter inch to 

 nearly half an inch in diameter, and again gradually diminishing toward the apex, 

 which is of equal tenuity with the base. This threadlike frond is cylindrical, hollow, 

 divided at short intervals by very thin membranes, into chambers or joints, which 

 are not visible externally ; it is slimy to the touch, and clothed, at an early stage, 

 with very dense, slender, gelatinous filaments, which generally disappear as the plant 

 advances to maturity, but may sometimes be found on old plants, especially on 

 such as grow in quiet, deep bays where they are little exposed to the action of 

 waves. The substance is cartilaginous and firm, and very tough when recent. The 

 fructification covers the whole external surface of old plants, and consists of obconical, 

 vertical spores, supported on long pedicels, by which they are attached to the outer 

 row of cellular tissue. Mixed with these are found numerous, narrow, elliptical, 

 transversely striated cells, which may be antheridia. The walls of the tubular 

 frond are formed of several rows of hexagonal, elongate cells, placed end to end, 

 and forming longitudinal threads, glued together by the sides. Of these the inner 

 ones are of large size ; the outer, minute and more densely packed together. 



2. Chorda lomentaria, Lyngb. ; frond membranaceous, constricted at distant 

 intervals ; the interstices inflated. Lyngh. Hyd. Dan. p. 74, t. 18. Harv. Phyc. 

 Brit. t. 285. Chorda filum, ^. lomentaria, Kiltz. Sp. Alg. p. 548. Scytosijyhon 

 lomentarium, J. Ag. Sp. Alg. vol. 1, p. 126. 



Hab. On rocks and stones, &c. in tide pools. On the eastern coast, from British 

 America to Charleston, S. C. (v. v.) 



Root a small disc. Fronds from eight to twelve or eighteen inches in length, 

 tapering at the base to the diameter of horse hair, attenuated upwards, either to a 

 bluntish or a very fine point, from two to four lines in diameter at the greatest 

 breadth, cylindrical, constricted at irregular intervals and furnished with a trans- 

 verse septum at each constriction. The walls of the tube are composed of a thick layer 

 of large, polygonal cells, of which the outer ones are gradually smaller ; on the outside 

 of which, forming the periphery, is a stratum of radiating, close-packed, moniliform 



