226 ALG.^ 



by the lifting up of a lid, and which impregnate the oospheres in the 

 usual way. 



A\'hen the hypnosperm germinates after a lengthened period of rest, 

 it does not immediately develop into a new plant, but breaks up into 

 several zoospores, usually four ; these give birth to several generations of 

 non-sexual plants, until the cycle is completed by the production of 

 antherids and oogones. The sexual plants, however, especially the female 

 ones, produce zoospores as well. 



The species of i5///^^(r/^(^/<? (classed by some writers with Coleochoete) 

 are minute plants growing in fresh water, and differing from CEdogonium 

 in having branched filaments ; the terminal cells of the branches 

 ending in long hyaline bristles, which are swollen at the base. The 

 modes of reproduction correspond closely to those in CEdogonium. 

 Wittrock includes also Coleochaete and Sphceroplea among the CEdo- 

 goniacese. 



Literature. 



Braun — Verj. in der Natur, 1851 (Ray S(;c. Bot. and Phys. Mem., 1853). 



De Bary — Ueber QEdogonium u. Bulbochaete, 1854. 



Pnngsheim — Jahrb. wiss. Bot., 1858, p. i. 



Carter— Ann. and Mag. Nat. Hist., 1858, p. 29. 



Juranyi — Pringsheim's Jahrb. wiss. Bot., 1873, p. i. 



Wittrock — Prodr. Monogr. QEdogoniearum, 1874. 



WiHe— Pringsheim's Jahrb. wiss. Bot., 1887, pp. 443 and 454. 



Order 3. — SPH^EROPLEACEiE. 



This order comprises at present the single species Sphceroplea 

 annulina Ag., the simplest of the class, found occasionally on flooded 

 fields. The filaments are cylindrical and unbranched, and are composed 

 of cells which vary in their comparative length and breadth to an extra- 

 ordinary degree ; sometimes the length will hardly exceed the breadth, 

 while in other cases it may be as much as ninety times as great. The 

 transverse cell-walls are of great thickness, their surface is irregularly 

 wavy, and they swell out here and there into great ' beams ' and excres- 

 cences of cellulose from both the lateral and longitudinal walls. During 

 the development of these septa, orifices are formed in them for the 

 passage of the antherozoids. The cells contain a large number of 

 chromatophores and starch-grains, as well as, when mature, a consider- 

 able number of small nuclei. 



The sexual reproductive elements are oospheres and antherozoids, 

 formed in different cells of the same filament, which may therefore be 

 regarded as rudimentary oogones and antherids. A filament may consist of 



