226 INTRODUCTION TO CRYPTOGAMIG BOTANY., 



different as to seem to indicate totally distinct species. Thejr 

 are indifferently Algae of the northern and southern hemi-, 

 spheres; and some species, as Bichloria viridis and BesTua- 

 restia ligulcda, are found in both. Of our British species, 

 Arthrocladia villosa extends as high as Scotland, hut 

 Sporochnus pedit,nculatus and Garpomitra Cabrcrcc, a 

 very rare if a true inhabitant of our seas, are southern, 

 plants. 



210. They form two evident groups distinguished by the 

 freedom or compactness of the fruit-bearing threads. The 

 antenna -form threads of spores in Arthrocladia are very 

 beautiful. In Desmarestia the fruit at present is unknown, 

 though some of the species are extremely common. In the 

 broader forms of D. ligulata, the fronds are distinctly nerved, 

 and sometimes resemble leaves, in consequence of the se- 

 condary nerves, as in that found at Loch Swilly. Chnoo- 

 spora, which is essentially tropical, is remarkable for its dicho- 

 tonaous fronds. None of the species of the second group have 

 at present been found in America ; but dredging may yet 

 detect individuals which have hitherto escaped notice. Few 

 Algae are more beautiful than Sporochnus pedunculatus, 

 when the pear-shaped fructifying branches are terminated by 

 their tufts of threads. The mitrseform receptacles of Garpomi- 

 tra Gabrerce, situated at the tips of the branches, give a sin- 

 gular appearance to the frond, from the peculiar way in which 

 they are seated. Arthrocladia villosa, when placed upon 

 paper, makes it transparent as if dipped in oil,* and Desma- 

 restia ligulata and herbacea have the same property. 



6. FucACEiE, Ag. 



Inarticulate ; spores contained in elliptic or spherical con- 

 ceptacles, sunk in the frond. Impregnation by spermato- 

 zoids. 



211. We now come to one of the most important tribes of 

 seaweeds, which seem in many respects to deserve the hioh 



* It was in consequence of this proi^erty, that I named the genus 

 Arthrocladia, EhdoneiTna. The name Arthrocladia was proposed two or 

 three months previously by M. Duby. 



