22 SPOKOCHNACE^. 



receptacles are attached the spores, which are generally 

 pear-shaped, containing a single mass, lodged in a pellucid 

 peiispore. The antheridia are unknown, 



A small group, of which five (or, according to the views of 

 some authors, six) genera, comprising twenty-four species, 

 are at present known to botanists. Notwithstanding such a 

 discrepancy in the organs of fructification as obliges us to 

 break the order into two families, yet there is so much simi- 

 larity in the structure and habit of these plants, and all so 

 closely agree in the remarkable property of changing them- 

 selves from olive to a verdigris colour, and then causing the 

 rapid decay of all delicate Alga brought into contact with 

 them, that I cannot but regard the assemblage as a natural 

 one. Their power of destroying other Alga? has long been 

 known, and another curious property, first observed in Ar- 

 throclaclia, is common to many, namely, that of rendering 

 paper for the moment transparent, as if the branches gave 

 out an oil. This acts but temporarily, ceasing when the 

 plant is perfectly dry. 



The Sporochnacece are chiefly characteristic of cold or 

 temperate latitudes, between the parallels 64° and 40°. One 

 genus, Chnoospora, is tropical. Arthroclndia appears to be 

 confined to the shores of Europe. Of seven species of Des- 

 marestia, four are known only in the higher latitudes of the 

 Southern Ocean, while the other three, our British species, 

 are dispersed throughout the Atlantic and Pacific, both 

 North and South. D. mridis is excessively common in the 

 Antarctic Ocean, and D. ligulata is found on the N. West 

 coast of America, at the Cape of Good Hope and at Cape 

 Horn. Of six species of Sporochnus, three belong to the 

 shores of Europe, and three to those of Australia. Of Car- 

 pomitra four species are known, all of them found on the 

 Australian coasts, three of them exclusively so ; the fourth 

 (our C. Cabrerce) is a native of New Zealand, of the south of 

 Spain, and of the south of England and Ireland. The dis- 

 tribution of this last-named species is very singular, particu- 

 larly as it seems to be rare in all its recorded stations. 



None of the species are used in the arts. 



