THE MARINE ALG.E OF NEW ENGLAND. 91 



cylindrical; fructification in broad bands or large irregular spots, or 

 occasionally covering the whole surface of frond, composed of large 

 broadly clavate or wedge-shaped paraphyses and oval unilocular spo- 

 rangia. 



Fronds cylindrical Chorda. 



Fronds with a midrib. 



Fronds perforated with holes Agarum. 



Fronds entire, with lateral leaflets at the base of lamina Alaria. 



Fronds destitute of midrib. 



Cryptostomata present r Saccorhisa. 



Cryptostomata wanting , . Laminaria. 



OHOEDA, Stack. 



(From chorda, a string.) 



Fronds olive-brown, attached by a disk, simple,' cylindrical, hollow, 

 with diaphragms at intervals ; cells of tubular portion elongated, hex- 

 agonal in section, lined on the inside with filaments, which at intervals 

 are woven together so as to form the diaphragms; whole surface of 

 the frond clothed with cuneate-clavate cells (paraphyses), which form a 

 cortical layer; unilocular sporangia ellipsoidal, situated between the 

 paraphyses, growth basal ; plurilocular sporangia unknown. 



A small genus, consisting of three or four species, which arc by some writers placed 

 in the Chordariacece and by others in the Laminariacece. The typical species, C. filum, 

 may be regarded as the lowest representative of the Laminariacece, inasmuch as it has 

 the basal mode of growth and the unicellular paraphyses of that order, but a simple 

 frond in which there is no distinction of stipe and lamina. See, also, remarks under 

 Scytosiphon. 



C. filum, Linn. (Scytosiphon filum, Ag. — Chorda filum, Phyc. Brit., 

 PI. 107 ; Annales des Sciences, Ser. 3, Vol. XIV, PL 20, Figs. 5-10.) 

 PI, VI, Fig. 1. 



Fronds gregarious, cartilaginous-lubricous, quarter of an inch in diam- 

 eter, from one to twelve feet long, attenuate at base, densely clothed 

 with hyaline hairs ; paraphyses cuneate-clavate, slightly longer than the 

 sporangia and overlapping them. 



On stones at low- water mark and below. 



Common along the whole coast ; Europe. 



At once recognized by its cord-like appearance. The early form, which is densely 

 covered with hairs, constitutes the C. tomentosa of some writers. Areschoug, however, 

 considers that the true C. tomentosa of Lyngbye is distinct, and characterized by its 

 elongated linear paraphyses, which are scarcely as long as the sporangia, which ripen 

 early in the season, while those of C. filum ripen in the latter part of summer and 

 autumn. 



