CONFERVOIDE.E ISOGAM.E 



279 



Hansgirg (Bot. Centralblatt, 1885) believes that the filamentous genera 

 placed in this genus are connected genetically with forms classed under 

 the Chaetophoracese, Siphonocladacese, and Ulvaceae. To this order 

 belong also Hormidium (Ktz.) and Schizogonium (Ktz.). "Wildeman 

 (Bull. Soc. Bot. Belg., 1886, p. 7) traces a genetic connection between 

 Ulothrix and Pleurococcus. 



Literature. 



Cramer — Vierteljahrschrift Nat. Gesell. Zurich, 1870. 



Cienkowski — Mel. biol. Bull. Acad. St. Petersbourg, 1876, p. 531. 



Dodel-Port — Pnngsheim's Jahrb. wiss, Bot., 1876, p. 417; Bot. Zeit., 1876, p. 177. 



Gay — Bull. Soc. Bot. France, 1S88, p. 65. 



Hansgirg — Flora, 1888, p. 259. 



Order 4. — Chroolepide.^. 



This order, as constituted by Borzi, comprises a small group of 

 algae found on damp walls, the trunks of trees, and similar situations, 

 not unfrequently imbedded in the thallus of lichens, or constituting their 

 gonidial element. The thallus consists of a branched or unbranched 

 filament of cells, usually 

 somewhat rounded or mo- 

 niliform in outline, and is 

 distinguished by the mask- 

 ing of the colour of the 

 chlorophyll by a golden 

 yellow, orange, or red oily 

 pigment, soluble in alcohol 

 and imparting a strong 

 odour of violets. This pig- 

 ment, which occasionally 

 occurs also in other lowly 

 organised algae and proto- 

 phytes, has been examined 

 by Rostafinski, and found 

 to be a derivative of chlo- 

 rophyll to which he gives 

 the name chlororufi?i. 

 Microzoospores or zooga- 

 metes and megazoospores 

 are produced in gametanges 

 or zoosporanges, which are 



indistinguishable from the vegetative cells except by their somewhat larger 

 size, and which are either terminal or intercalary. Conjugation of the 



Fig. 247. — Tt-cntepohlia Bleischii Rbh, A, filament with 

 swollen cells in which the zoogametes are formed (game- 

 tanges), g; B, stages in the conjugation of the zoogametes 

 ( X 330). (After Wille.) 



