EISENIA ARBOREA. 131 



habitat of the specimen. It is usually composed of a con- 

 siderable number of rather slender hapteres, several times 

 dichotomously branched, the ultimate branchlets being very 

 fine, numerous, and contorted. The diameter of the entire 

 holdfast is generally considerable, reaching, or perhaps even 

 exceeding 25 cm. The attachment is made to stones or angu- 

 lar projections from the larger rocks, and specimens often 

 must needs be removed from the substrata by the aid of the 

 knife. The specimen figured in Plate 4 shows a typical and 

 very well-developed holdfast. 



The hapteres themselves arise from the very base of the 

 stipe in three or four fairly regular whorls. A cross section 

 of a single haptere shows a rather irregular circle of mucilage 

 ducts lying at some distance within the periphery. The 

 ducts seem to be more abundant in that portion of the haptere 

 situated away from the substratum than in that directly adja- 

 cent to it. 



B. Stipe. 



The stipe varies in length according to the age of the indi- 

 vidual. Areschoug's largest specimen possessed a stipe 28 

 cm. in length. In the largest specimen seen by the writer, 

 the stipe was about 60 cm. long. It is fairly stout and rigid 

 and remains nearly erect when the plants are left partially 

 bare by the fall of the tide and projects above the surface of 

 the water bent more or less under the weight of the heavy mass 

 of sporophylls at the top. The stipe approximates to terete 

 at the very base but soon becomes somewhat compressed, 

 and this increases until at the top it is very decidedly flat- 

 tened. 



The medullary portion is flattened, even at the very base, 

 while above it soon becomes narrowly linear in cross section. 

 The whole internal structure is very dense and there is a row of 

 mucilage ducts situated in the outer cortex. This line of ducts 

 is nearer the medulla at the middle of the sides of the flattened 

 portions and nearer the periphery at the ends. 



