20 EXPLANATION OF THE PLATES. 



Fig. 18. Pediastrum simplex. — Fig. 19. Pediastrum ele- 

 gans. 



PLATE LXXXVIL 



Fig. 1. Closterium Ehrenbergii. — Fig. 2. Closterhim monili- 

 feram. — Fig. 3. Closterium turgidum. — Fig. 4. Closterium 

 striolatum. — Fig. 5. Closterium acerosum. — Fig. 6. Clos- 

 terium rostratum. — Fig. 7. Closterium setaceum. 



PLATE LXXXVIII. 



Fig. 1. Closterium lineatum. — Fig. 2. Closterium Cornu. 



— Fig. 3. Closterium Trabecula. — Fig. 4. Closterium Digi- 

 tus. — Fig. 5. Closterium margaritaceum. 



PLATE LXXXIX. 



Fig. 1. Xanthidium furcatum. — Fig. 2. Xanthidium fascicu- 

 latum ? — Fig. 3. Xanthidium acideatum ; a, front view; b, 

 end view ; c, side view ; d, new segment. — Fig. 4. Xan- 

 thidium polygonum. — Fig. 6. Tetmemorus granulatus : a, 

 front view ; b, side view ; c, empty frond ; d, fronds con- 

 jugated, showing mode of formation of the sporangium; e, 

 sporangium perfectly formed. — Fig. 5. Tetmemorus Bre- 

 bissoni : a, front view ; b, side view ; c, empty frond ; d, 

 segment of frond. 



PLATE XC. 



Fig. 1. Micrasterias rotata: a, adult frond ; b, c, young fronds 

 of same ; d, showing the mode of formation of the new 

 segment. — Fig. 2. Micrasterias radiata. — Fig. 3. Holo- 

 cystis oscitansf {Euastrum crux melitensis, young, Ehr.) — 

 Fig. 4. Holocystis oscitans. — Fig. 5. Euastrum circulare. 



— Fig. 6. Euastrum. — Fig. 7. Micrasterias crux melitensis 

 {Euastrum crux melitensis Ehr.). — Fig. 8. Euastrum Di- 

 delta : a, front ; b, side view. — Fig. 9. Euastrum affine; a } 

 front ; b, side view. — Fig. 10. Euastrum. 



