(120) 



Although scarcely so complicated in its structure as the preceding, its 

 regularly located filaments form a beautiful object under the microscope, 

 the cells being only of two distinct forms; those of which the central 

 filaments are composed being cylindrical, those of the periphery spherical. 



In habit, too, it is much more crustaceous than the preceding, being 

 closely appressed to the rock, to which it is firmly attached by its whole 

 under surface, and never, so far as we have been able to learn, found 

 parasitical. 



LEATHESIA BERKELEY!. 



EXPLANATION OF DISSECTIONS. 



Fig. 1. — Section of frond. 

 2. — Filaments of same. 



Both magnified. 



