124 SIPHOPHYCE.E. 



sponge, with its surface beset by erect branches which give it a very 

 bristly appearance. In this state it is well known to botanists as the 

 C. amphibia of all modern authors. Its hue is of a bright green, 

 becoming ash-coloured with age. The root I have not been able to dis- 

 cover, and the entangled mode of its growth renders it impossible to 

 ascertain the length of the filaments. These are repeatedly divided with 

 distinct patent branches, which, as before mentioned, when the plant 

 grows in shallow water, so that some of them are exposed to the air, send 

 out patent ramuli, of a stunted growth, from being out of their proper 

 element, which by their erectness give the plant its bristly appearance; 

 yet at the same time, if whilst in this state the waters rise so as to over- 

 flow the plant, their length is gradually increased, and losing their erect 

 position they yield to the current, and become the Geranium ccespitosutn 

 of Roth ; and after having thus changed, if by the subsidence of the 

 waters the surface is again exposed to the air, the filaments, of course 

 disposed horizontally, give the plant a bristly appearance by again throw- 

 ing out erect patent ramuli." 



var. oxnithocephala. Hassall Alg. t. 6, /. 4. 



In dirty green tufts, densely imbricated, and becoming paler. 

 Thallus loosely branched. Oogonia solitary, or in pairs, oval- 

 oblong, obliquely rostrate, beaks truncate, antheridia cylindric- 

 subulate, incurved, interposed, usually exceeding in length the 

 diameter of the oogonia. 



Vaucheria ornithocephala, Eng. Fl. v., 320. Harv. Man. 

 148. Hook. Fl. Scot, ii., 93. Eng. Bot. ii., p. 195. Grev. 

 Alg. Britt. 190. Grev. Fl. Ed. 306. Fl. Devon, ii., 56. 

 Gray Arr. i., 291. 



Conferva vesicata, Dillw. Conf. t. 74. 



In stagnant or slow-flowing water. 



var. rep ens. Hassall Alg. t. 6, /. 7. Ann. Nat. Hist. XL, 430. 



Terrestrial. Oogonia single, sessile, oblong or ovate, shortly 

 rostellate, mouth lateral, truncate. Antheridia solitary, next 

 the oogonium, cylindric-clavate, erect, inclined or curved, 

 scarcely longer than the oogonium. 



On the naked ground. 



It is on Vaucheria sessilis that Sir J. E. Smith says are found th 

 " Vesicles of the nature of galls, perhaps, inhabited by Muller's Cyclops 

 lupula" figured on plate 2419 of the second edition of English Botany. 

 Hassall states that the species is V. geminata, but this is accounted for 

 by the belief which was current in those days that V. geminata was the 

 summer form of V. sessilis. See Eng. Bot. ed. n., p. 125. 



Plate XLVI., figs. 1 to 20. Impregnation of Vauclieria sessilis, after 

 Pringsheim X 200. 



Plate XLVIII., fig. 1, part of thread, with sexual organs, of V. sessilis. 

 Fig. 2, oogonia and antheridia X 200. Fig. 3, oogonia and antheridium 

 of the variety ccespitosa X 300. Fig. 4, oogonia and antheridium of the 

 terrestrial variety repens X 200. Fig. 5, threads bearing sporangia at the 

 tips slightly magnified. 



