ALGJE. 



451 



finite or indefinitely great, on account of more advanced segmentation of 

 the contents. The mode of reproduction and the forms of the thallus in 

 such genera as JSctocarpus &c. bring this Order very near to the Con- 

 fervoidese. Much obscurity still prevails here, since antheridia coexist 

 with reproduction by zoospores in Cutleria, and appear to exist in Spha- 

 celaria and Cladostephus, which also reproduce by zoospores. 



Distribution, Qualities, &c. Much the same as in Fucaceae. Laminaria 

 digitaia and saccharina are eaten (under the name of Tangle) on the coasts 

 of the north of Europe, as also is Alaria esculenta. 



CONFERVOIDE^. SILK-WEEDS. 

 Class Algge, Endl. All Algales, Lindl. 



Diagnosis. (Fig. 512.) Plants with a filamentous, membranous, 

 gelatinous, or pulverulent thallus, growing in fresh or salt water, 

 or on moist substances, of a bright green or, more rarely (often 



Fig. 512. 



Organization of Confervoid Algae : A. Filaments of Spirogyraquinina: a, in natural condition 

 ( magnified 50 diameters) ; 6, two filaments conjugating ; c, a spore formed in one cell from 

 the mixed contents ; d, a free spore ; e, the same germinating. B. Protococcus viridis 

 (magn. 200 diameters): a, a group of cells cohering by jelly-like matter; b, four cells 

 formed by division of a cell of a, and two zoospores escaped from one of the cells, sub- 

 sequently settling down as resting-cells, c. C. Cladophora fflomerata : a, filaments, of 

 natural size ; 6, the top of a branched filament, magnified; c, cells about to form zoo- 

 spores ; d, the same, with the zoospores escaping from the uppermost cell ; e, zoospores 

 germinating into new filaments. 



