THE MARINE ALG.E OF NEW ENGLAND. 97 



The plant is perennial and young specimens are entirely -without perforations until 

 they have attained a length of two or three inches. The perforations, which are 

 supposed by the fishermen to be the work of animals, are formed in the lower part of the 

 frond and increase in size, as they grow older, so that the perforations are larger in 

 the upper and central parts of the frond. "New holes are also formed between those 

 already formed, so that there is a difference in size depending upon the age of the holes 

 in all parts of the frond except the base. The formation of the holes begins by an 

 elevation of small portions of the frond, which appears as if some small point like that 

 of a pencil had been pressed against it ; at length the frond ruptures circularly and 

 the hole formed is minute and above the plane of the frond. The margins of the large 

 holes are often wavy, and when dried with a slight pressure the waviness becomes so 

 marked as to lead one to suppose that the specimens belong to a distinct species. The 

 midrib varies considerably in breadth and occasionaly it grows out, forming a lamina 

 at right angles to the frond. The usual perforations are found in the additional 

 lamina, which sometimes grows to be as large as the original lamina. The fruit of 

 Agarum, which is incorrectly figured in the Nereis as having a form of tetraspores, 

 resembles very closely that of Laminaria. The species apparently does not bear fruit 

 on the Massachusetts coast, at least we have never been able to find any ; but at East- 

 port the fruit is formed as early as September. The sori are scattered irregularly over 

 the central part of the frond and are most easily seen after the frond has been out of 

 the water a short time. The sori are not so thick as in Alaria and Laminaria and the 

 paraphyses do not have so prominent a hyaline extremity as in those genera. Harvey 

 states that the lamina are sometimes ten or twelve feet long, but this- is probably an 

 overestimate. 



ALARIA, Grev. 



(From a la, a wing.) 



Fronds attached by a branching root-like base, stipitate, membrana- 

 ceous, with a distinct midrib ; fruit borne in special lateral leaflets below 

 the lamina, consisting of club-shaped, one-celled paraphyses and ellip- 

 soidal unilocular sporangia ; plurilocular sporangia unknown. 



A genus readily known by the small, ribless leaflets given off from the stipe below 

 the lamina, in which the the fruit is borne in the autumn. The genus inhabits the 

 colder waters of the northern hemisphere and the species sometimes attain a length of 

 fifty feet. The number of species does not exceed half a dozen, and the specific marks, 

 such as the shape of the midrib, the lateral leaflets, and the base of the lamina, are 

 variable, so that all the species cannot be said to be well marked. 



A. esgulenta, Grev. (A. esculenta, Phyc. Brit., PI. 79. — Laminaria 

 muscefolia, De la Pyl., Ann. Sci. ISTat., Ser. 1, Yol. FV, PI. 9 d. — L. linearis, 

 DelaPyl., L c, PL 9/.) 



Stipe cylindrical-compressed, from four inches to a foot long, a quarter 

 to half an inch wide; midrib solid, scarcely wider than the stipe; lam- 

 ina one to ten feet long or even longer, two to ten inches from side to 

 side, decurrent on the stipe, margin wavy ; fructiferous leaflets numer- 

 ouse, shortly stipitate, three to eight inches long, half an inch to two 

 inches broad, linear-ovate or linear- spathulate. 



Var. latlfolia, Post. & Rupr. (Laminaria Pylaii, Bory, in Flore 

 8. Miss. 59 7 



