No. 3] REMARKS ON NORTHERN LITHOTHAMNIA. 45 



develops any crustaceous hypothallus. Among a large number of 

 specimens I have only seen a single one attached to the substratum 

 with a small crust very faintly developed, while elsewhere the alga 

 is lying freely on the bottom. The apparent hypothallus which is 

 now and then seen in old specimens are only remnants of parts 

 of the alga which have fallen to decay, partly on account of attacks 

 of animals, partly because of the friction of the water. , Such 

 lingering remnants are often covered with crusts of the same spe- 

 cies faintly developed, from which new branches are developed — 

 in part and particularly with crusts of other species, e. g. L. fla- 

 vescens. Cp. Norw. Lithoth., pi. 8, fig. 1. 



In N. Ish. Algfi. 1. c. Professor Kj ell man identifies L. TIngeri 

 with L. byssoides Unger, Leithakalk p. 19—20, t. V, fig. 1 — 8, 

 the latter from a specimen collected in the neighbourhood of Ber- 

 gen. I have formerly pointed out that they are scarcely identical, 

 but that L. byssoides must be referred to L. nodulosum. Cp. 

 Norw. Lithoth. p. 29 and 6i. ■ 



The alga in question is generally attacked by boring mussels 

 at an early stage of development, and in certain localities it is at 

 the same time worn by friction of the water. Accordingly the 

 central parts of the alga, which have partly fallen to decay, often 

 convey the impression of forming rather coarse lobes such as are 

 mentioned in Norw. Lithoth. But this is only due to a fusion of 

 branches which has taken place at an earlier stage. The alga 

 will finally get hollow, the outer branches more coalescing than 

 usual, and at the same time large surfaces of friction being formed. 

 From such parts worn are often developed a number of wartlike 

 processes or short branches. Cp. Norw. Lithoth. pi. 4, fig. 1 — 2. 



The form corymbiformis 1. c. pi. 6 represents such old spe- 

 cimens of the species, much dissolved and worn, but partly 

 emitting new bundles of branches. I, therefore, do not maintain it 

 as an independent form. If the interior of the alga is attacked by 

 animals, and the outer parts are not at the same time worn by 

 friction, the branches become here still more approximate, less 

 curved and more coalescing than elsewhere. In such cases, the 

 plant is hardly distinguishable from L. fornicatum f. subphcerica 



