8 HANDBOOK OF SEA- WEEDS. 



by their flinty shells, which are often beautifully sculptured. 

 Their endochrome is a golden brown, instead of green as in the 

 Desmideacese. The latter, also, are confined to fresh water, while 

 the Diatomacese are found, though not exclusively, in the sea, 

 where their shells sometimes, microscopically minute as they are 

 individually, form banks extending several hundred miles. It is 

 stated that in the collection made by Sir Joseph Hooker in the 

 Himalayas the species closely resemble our own. 



In the next group, Confervaceae, we are introduced to forms 

 more like the general notion of what a plant should be. The 

 individuals of which it consists are composed of threads, jointed, 

 either simple or branched, mostly of a grass-green colour, and 

 propagating either by minute zoospores or by metamorphosed 

 joints. They are found both in fresh and salt water, and in 

 damp situations. The number of species is very great. 

 A considerable number consist of unbranched threads; the 

 branched forms grow sometimes so densely as to assume the 

 form of solid balls. After floods, when the water stands for 

 several days, they sometimes increase to such an extent, as to 

 form on its subsidence a uniform paper-like stratum, which while 

 decomposing is extremely disagreeable. The name Conferva 

 has been almost discontinued as a generic title, the majority of 

 British species being now ranged under Clado- and Chseto-phora. 

 The latter are branched, and require great care and attention in 

 order to distinguish them, on account of their general resem- 

 blance to each other. Good characters are however to be found 

 in their mode of branching and the form and comparative size 

 of the terminal joints. 



The Batrachospermeze constitute a small but very beautiful 

 group, consisting of gelatinous threads variously woven into a 

 branched cylindrical frond. The branches are sometimes ar- 

 ranged, as in the British species, so that the plants appear like 

 necklaces. In colour they pass from green, through intermediate 

 shades of olive and purple, to black. In common with some of 

 the higher Algce, the threads of the superficial branches send 

 joints down the stem, changing it from simple to compound. 

 The native species are all fluviatile. 



The Hydrodicteee are among the most remarkable of Algae. 

 Hydrodictyon utriculatum, the solitary British species, is found 

 in the large pond at Hampton Court, and in similar situations 

 in various parts of the country, but not very generally. It re- 

 sembles a green purse or net, from four to six inches in length, 

 with delicate and regular meshes, the reticulations being about 

 four lines long. Its method of reproduction is no less remarkable 



