INTRODUCTION TO CRYPTOGAMIC BOTANY. 



201 



southern hemisphere. Bostrychia vaga, in the cold climate of 

 Kerguelen's Land, may be traced from rocks and stones, about 

 high-water mark, to a considerable distance inland. The tips 

 of its threads are often curled, which makes them peculiarly- 

 apt to be entangled with other plants. Tliough Dasya elegans 

 is equally common in America and southern Europe, while its 

 near relative, B. villosa, abounds in Van Diemen's Land, the 

 European D. coccinea is not known on the eastern North 

 American coast ; and its nearest ally is found on the Western 

 Pacific shores, at Puget's Island, from whence it was brought 

 by Captain Wilkes's expedition. Rytvpldwa is a rare inhabi- 

 tant of our southern coasts. The genera are far more abun- 

 dant in the southern than in the northern hemisphere. Eleven 

 genera only occur on the eastern coast of North America, 

 including Ohondria, and some of them are sub-tropical, while 

 in the Southern Ocean there are at least twenty-three. 

 Amansia, Alsidium, Acanthophora, and Digenea, are 



Fig. 49. 



Polyzonia cuneifolia, Mont., with stichidia, conceptacle, and spores, 

 magnified. From specimens communicated by Dr. J. D. Hooker. 



unknown upon our coasts, and delight in a warm climate. 

 They occur, therefore, in such tracts as the Red Sea; wliile, on 

 the contrary, Odoiithalia is a genus of high latitudes. Though 

 so common in some parts of the Scottish coast, it is wholly 



