244 MELANOSPERMEJE. PA.RT n. 



The MELANOSPERME^E, or Melanosperms, are olive- 

 green Algse, sometimes inclining to brown. They have 

 fewer species than the Rhodosperms, but the indivi- 

 duals exceed in abundance and in magnitude all the 

 other Algse. 



These large Melanospermous Algae, which form marine 

 forests in both hemispheres, are excessively strong and 

 tough on the exterior but of a looser texture within, so 

 that the cells of their tissue are of different sizes and 

 forms, according to the degree of pressure. The stems and 

 branches are more dense than the leaves. This highest 

 order, however, has small and delicate Algse united to 

 the largest by many intermediate forms. The Melano- 

 sperms are either monoecious or dioecious, and bear their 

 olive-green spores in cases, that is cysts, variously dis- 

 posed on the plants. Many have two kinds of zoospores 

 differing in nothing but size ; they are produced in 

 different organs; in some species both are fertile, in 

 others only one, and, in these cases, the other is there- 

 fore supposed to be a fertilizing body, but however that 

 may be, there are certainly antherozoids in this group 

 of Algse, especially in the order Fucacese. 



The Ectocarpese have many representatives on our 

 coasts, all of which are tufts of articulated threads from 

 one to eighteen inches long, branched or simple. They 

 are generally soft, some so flaccid that they cling to- 

 gether, but sometimes they are firm and stiff. The cysts 

 which are attached to these threads have various forms ; 

 they are spherical, siliquose (that is, like long pods), or 

 of other shapes, according to the species ; but whatever 

 form they may assume, they are filled with a dense 

 endochrome. Besides these they have active granules 

 contained in other distinct organs. M. Thuret has 

 decided beyond a doubt that the latter are small 

 zoospores, and it is presumed that the endochrome in 

 the cysts is resolved into zoospores, but of a different 



