48 



different. They appear, so far as 1 have seen, to be distinguished 

 especially as to the shape and size of the conceptacles of sporangia. 



Remarh on the definition of the form. The present plant 

 includes numerous forms, the principal of which are quoted above. 

 A couple of these might perhaps be regarded as separate species, 

 but it has not been possible to draw any true limit, and I, there- 

 fore, regard them as forms of the species in question, to which 

 they appear at least to be closely related. 



Through the kindness of Mad. A. Weber van Bosse I have 

 had the opportunity to examine three specimens from Hauck's 

 herbarium of his L. fasciculatuui ft fruticulosum. One of these 

 fully accords with specimens in my collection of the above f. 

 typica. Cp. pl. 3. The second is a younger individual, probably 

 belonging to the same form. The third may perhaps also be re- 

 ferrible to this form, but on the other hand it rather reminds one 

 of L. nodulosum in habit, nor did I succeed in finding overgrown 

 conceptacles of sporangia. The form is somewhat varying, but in 

 general easily recognized. The branches more or less densely 

 crowded are in Hauck's as well as in my specimens generally 

 1.5— 2 mm. thick, rather anostomosing especially in older individu- 

 als, and frequently carrying short and wart-like or longer and 

 branch-like processes. Pl. 3 and Hauck 1. c. Much attacked by 

 boring-muscles it occasionally becomes more or less hollow and 

 opened in the lower part, but it apparently never assumes a cup- 

 shaped form like several other Lithothamnia. In old specimens 

 growing in shallow water with strong currents the upper branches 

 frequently become more or less denudated, or biten off, the rest 

 afterwards in part anastomosing, forming crustlike expansions, or 

 here and there with new branches in development. Pl. 3, fig. 6 

 and pl. 4, flg. 1 — 2. This form is in general to be found freely 

 developed on the bottom, seldom encompassing shells or smaller 

 stones. It attains a diameter of about 15 cm., more frequently, 

 however, about 10 cm. or less. 



The form fastigiata is nearly connected with the typical form. 

 Pl. 5, fig. 7 represents a specimen somewhat approaching the latter. 

 It also commonly develops freely on the bottom, sometimes fastened 



