On the Nucleus of Sphaerophoron and Lichina. 269 



Thamnophora, among the Byssacece, Lichina, and among the 

 Hypoxylece, Thamnomyces ; note however that I say genera 

 analoga, non autem affinia. 



The typical plant of the genus Lichina, first observed by 

 Micheli, was considered by him as a lichen. Linnaeus, and all 

 succeeding botanists, including Agardh, the founder of the 

 genus, have arranged it among the Phycecs ; not however 

 unanimously, for Acharius considers the second species of the 

 genus, L. confinis, Ag. (regarded as a variety only by Turner 

 and Hooker), as a lichen, and refers it to the Sphaerophoron. 

 In 1825 Fries established under the name Byssacece a family 

 intermediate between Lichenes and Phycece, and included in it 

 L. confinis, regarding L. pygmcea as a true Hydrophycea. Fries 

 recognises the affinities of Lichina with Collana, near which 

 he arranges it, and especially its resemblance to his own ge- 

 nus Synalyssa. 



But the two species cannot be separated nor placed in di- 

 stinct families ; for though their true nature be ambiguous, and 

 their systematic place necessarily uncertain, we can assert that 

 they possess the frond of the Fucacea and the fructifications 

 of Lichens. 



Turner, Lyngbye and Agardh, either through the imper- 

 fection of their instruments, or from other causes, have not 

 obtained right views of the fructification. Greville's descrip- 

 tion and figure (Algae Brit. p. 21, and Scot. Crypt. Fl. t. 219. 

 fig. 7-) are founded on a horizontal section of the fructifica- 

 tion. 



A thin longitudinal section of the mature apothecium of 

 Lichina pygmcea, viewed with a power of 600 diameters, shows 

 that the mucilaginous nucleus [lamina proligera) is composed 

 of extremely delicate, erect, flexuose filaments recurved and 

 crisped at their superior or free extremity. Their diameter is 

 at most ^o tn °f a millimetre, and their length varies between 

 Toth and TJ th of a millimetre. They are slightly swollen at 

 the summit, which is bent and somewhat recurved. In the 

 midst of these filaments we easily see the long thecae or utri- 

 cules in different stages of development. The shorter ones 

 contain only in the centre a shapeless greenish sporaceous 

 mass extending through nearly the whole length of the tube. 

 Others already enclose the sporidia, though their form is as 

 yet ill-defined. Others still more numerous exhibit these spo- 

 ridia in their perfect state. I presume that on their first for- 

 mation they are ranged in single series, but later some of 

 them are placed two and two, and thus render the theca dis- 

 tended in the part occupied by them. These thecae are shorter 

 than the filaments in the midst of which they are situated ; 



