256 



ALG.^ 



Literature. 



Reinke — Nova Acta Acad. Leop. -Carol., 1878. 

 Thuret & Bornet — Etudes Phycologiques, 1878. 

 Hauck — (Padina) Hedwigia, 1887, p. 41. 



The position of the small family of Syngenetice, as constituted by 

 Rostafinski, is one of great uncertainty. The two genera of which it is 

 composed have generally been regarded as of a very low type of structure, 



and it is very doubtful whether they are 

 nearly related to one another. The pro- 

 bability seems to be in favour of both 

 genera having been derived from the 

 Phaeosporeas by retrogressive metamor- 

 phosis in different directions. Heckel 

 and Chareyre (Journal de Microgra- 

 phie, 1885) regard Hydrurus and Chro- 

 mophyton as presenting a connecting 

 link between the Diatomaceae and the 

 Phceospore^. 



Hydrurus Ag. consists of a fila- 

 mentous thallus, attaining sometimes a 

 foot in length, slimy and affixed to a 

 conical disc, and growing in cold fresh 

 running water. The filaments are simple 

 below but branched above, often with 

 exceedingly fine penicillate divisions, 

 filled with a brown or olive endochrome 

 identical with phycophaein. The sur- 

 face is naked or densely covered with 

 delicate hair-like appendages, which are 

 occasionally fasciculate. The thallus is 

 composed of cells dispersed through 

 the gelatinous matrix ; towards the apex 

 of the branches the cells are in close 

 contact with one another, but in the 

 older parts of the thallus they are some 

 distance apart. Each is surrounded by 

 a very delicate membrane, and Lager- 

 heim states that some of them contain 

 pulsating vacuoles. Propagation takes place by means of zoospores of 

 very peculiar form, produced in the branches only, two or four from each 

 cell. When mature the zoospores are tetrahedral, each angle being 



Fig. 232. — A, Hydriims penicillatus Ag. 

 (natural size). (After Cooke.) B, zoo- 

 -spore (greatly magnified). (After Lager- 

 heim.) 



