ZYGNEMA. 143 



Z. nitidum, of which the filaments are larger ; the spires 

 too, are generally but three in number, and the sporangia are 

 less acutely oval, frequently also producing an inflation of the 

 cells in which they are lodged. 



8. ZYGNEMA CUKVATUM Ag. 

 Plate XXVI. Figs. 1, 2. 



Char. Filaments nearly equal in diameter to those of Z. neglec- 

 tum. Conjugation angular. Cells three or four times as 

 long as broad, coalescing without the intervention of trans- 

 verse tubes. Spires about four in number, faintly indicated. 

 Sporangia oval. 



Z. curvatum Ag. Conf. stritica, Eng. Bot. t, 2463. Harvey, 

 Hook. Br. Fl. p. 362., also in Manual. Mougeotia stritica 

 Kiitz. Alg. Dw. Sirogonium striticum Kiitz. Phyc. Gene- 

 ralis, p. 278. 



Hob. Ditches in Henfield Level, Sussex, and pools on 

 Chy -an Hal Moor, near Penzance: Mr. Borrer. Ches- 

 hunt: A.H.H. 



This species is remarkable for the direct conjugation of the 

 cells, they uniting with each other without the intervention 

 of tubes of communication, and it is the only species of the 

 genus which does so. By this junction of the cells with each 

 other, the filaments are bent at angles. The direct union of 

 the cells and angular flection of the filaments of this species 

 have induced Kiitzing to form a new genus for its reception 

 under the name of Sirogonium. Z. curvatum seems in some 

 measure to unite the genera Zygnema and Mougeotia, that it 

 is nothing more than a Zygnema, however, is proved by the 

 endochrome being disposed in a spiral order. 



9. ZYGNEMA PELLUCIDUM Hass. 

 Plate XXV. Figs. 1, 2. 



Char. Filaments of rather less diameter than those of Z. cur- 

 vatum, mucous, almost transparent. Conjugation parallel. 

 Cells six or seven times as long as broad. Spires indistinct, 



