276 ALG^E 



cell in certain conditions of Conferva. In this, and in the possession of 

 proteinaceous crystalloids (Klein, Bot. Zeit., 1880, p. 782), these genera 

 show an affinity to Siphonocladacese. Binuclearia (Wittr. ) (Bot. Centralbl., 

 xxix., 1887, p. 60) appears to have always two nuclei in each cell. 



There are still many points to be cleared up in the life-history of 

 the Confervaceae, although some of the genera are among the most 

 abundant of fresh-water organisms ; and the bounds and systematic 

 position of the family are still uncertain. According to some observers, 

 many of the species are connected genetically with forms at present 

 placed under the Protophyta ; to this view further reference will be 

 made hereafter. Andersson (Bot. Centralbl., xxxv., 1888, p. 351) believes 

 Palmella uvseformis (Ktz.) to be a resting condition of Draparnaldia. 

 Among the genera now included in the order are Conferva (L.), Micro- 

 spora (Thur.), Cladophora (Ktz.), Rhizoclonium (Ktz.), Stigeoclonium 

 (Ktz.), Chaetomorpha (Ktz.), Draparnaldia (Ag.), Chastophora (Schr.), 

 Urospora (Aresch.), and Binuclearia (Wittr.). Phseothamnion (Lagerh.) 

 (see under Syngeneticas) ought possibly to be included here; as also 

 Spongocladia (Aresch.) (see p. 290). Several species of Cladophora, 

 Chsetomorpha, and Rhizoclonium grow in brackish or even in salt water. 



Literature. 



Vaucher — Hist, des Conferves d'eau douce, 1803. 



Areschoug— Nova Act. Reg. Soc. Upsala, vi. , 1868, and ix. , 1874. 



Reinhardt— Arb. Naturf. Gesell. Charkoff, 1876. 



Wille — Bot. Centralbl., xi., 1882, p. 113 ; and Pringsheim's Jahrb. wiss. Bot., 1887, 



PP- 437. 459. and 492. 

 Lagerheim — Ber. DeutscH. Bot. Gesell., 1887, p. 409. 

 Murray and Boodle— (Spongocladia) Ann, of Bot., ii., 1888, p. 169. 



Order 2 (?). — Pithophorace*. 



The Pithophoraceae must be admitted as a distinct order only with 

 very great doubt, both because the mode of sexual reproduction is at 

 present unknown, and because of their strong resemblance to the Con- 

 fervaceae. The family, consisting of a single genus, was founded on 

 Pithophora Kewensis Wittr., an inhabitant of warm tanks in the 

 Botanic Gardens at Kew, Oxford, and elsewhere ; other species have 

 since been found in tropical America. The thallus is composed of 

 branching filaments of cells resembling Cladophora, but increasing only 

 by bipartition of the terminal cell, and presenting here and there barrel- 

 shaped cells very rich in chlorophyll, in which are formed resting-spores 

 of non-sexual origin. These germinate directly, and in opposite direc- 

 tions, from the two apices. There is another mode of non-sexual pro- 

 pagation by ' prolific cells ' ; but no zoospores nor any sexual mode of 



