949 



DESCRIPTION OF THE ENGRAVINGS. 



PLATE I. (Desmids). 



Figures 1 to 14. Cosmarium margaritiferum, &c., under different stages of develop- 

 ment: 1,2. Frond, enclosing "vesicles "filled with moving granules; 3. Supposed early state 

 of moving granules ; 4. Early stage of self-fission ; 5. Fission-products escaping the enclosing 

 wall of parent cell ; 6. Separation completed ; 7. Sporangium still connected with parent 

 frond ; 8. Same with mammilliform spines ; 9. Sporangium further developed ; 10, 11. 

 Supposed mature sporangia ; 12. Same, broken and empty ; 13, 14. Young supposed 

 products of sporangial contents : all after Mrs. Thomas, TM. 1855. [We are disposed to 

 think that one or two other species besides Cosmarium margaritiferum are here confounded. 

 4, we suggest, may possibly be C, caelatum or C. cristatum, showing nascent segments ; 

 7, C. Broomei, the empty frond to the right showing a segment not yet fully developed ; 

 8 and 9 appear to us as probably more likely to represent the conjugated state and sporan- 

 gium of C. bioctdatum, of which figs. 10, 11, 12, may represent the ultimately extruded 

 inner membrane, while figs. 13 and 14 may truly be the young fronds developed from their 

 contents, and which have not yet commenced vegetative self-division.] 15-17. Sphaero- 

 zosma vertebratum (Ealfs) : 15. A portion of a filament seen in f. v. X 200 ; 16. tr. v. 

 X400 ; 17. s. V. X400. 18, 19. Micrasterias papillifera (Breb.) : 18. f. v. X 100 ; 19. Spo- 

 rangium x200. 20. M. rotata (Ealfs), f. v. xlOO. SI. M. radiosa (Ag.), f. v. xlOO. 

 22. M. Crux-MeUtensis (Ealfs), f. v. xlOO. 23-25. Euastrum Didelta (Ealfs): 23. f. v. 

 with endoclarome ; 24. e. f. in f. v. ; 25. tr. v. : all x200. 26, E. rostratum (Ealfs), f. v. 

 X400. 27, 28. Xanthidium armatum (Breb.) : 27. f. v. ; 28. s. v. : both x200. 29, 30. 

 Arthrodesmus octocornis (Elu\): 29. var. j3, f. v. ; 30. var. a, f. v. : both x400. 31-34. 

 Staurastrum cuspidatum (Breb.) : 31. f. v. ; 32. showing the nascent segments ; 33. tr. v. ; 

 34. e. v.: all x400. 35,36. Ankistrodesmus falcatus (Ealfs), x400. 37-39. Sceno- 

 desmus obtusus (Meyen), after Nageli, showing segmentation of the cell-contents, x300. 

 40-42. S. caudatus, after Nageli, x300. 43. Same, segmentation of cell-contents, x400. 

 44,45. A few marginal cells of " Pediastrum Seleneea (Kg.)" = P. pertusum (?), after 

 Nageli, x300. 46-48. P. (Anomopedium) integi-um (Nag.): 46. xloO; 47. x400; 

 48. s. V. x400. 49-51. Coelastrum sphajricum (Nag.): 49. x200; 50, 51. X300. 

 52. Pediastrum Ehi-enbergii (Braun), after Braun, x400. 53. P. Selenaea (Kg.) [non 

 Ealfs, = P. pertusum], after Nageli, Xl50. 54, 55. Coelastrum cubicum (Nag.), after 

 Nageli, x300. 56-58. Sorastrum spinulosum (Nag.): 56. x300; 57, 58. x600. 

 59-61. Pediastrum Boryanum, var. brevicornis, after Braun : 59. Two marginal cells, 

 one empty, the other discharging the original inner membrane closely investing the micro- 

 gonidia; 60. The same half an hour afterwards, coiisiderably dilated, the microgonidia 

 each with a pointed hyaline beak, and at first slowly moving ; 61. Microgonidia, 

 eventually emitted, swimming freely: all x300. 62. P. granulatum (Kg.). 63. Brood 

 of macrogonidia emerged from shell of old frond, x400. 64. A few marginal cells of an 

 old frond, some empty, the cell-contents of others undergoing previous segmentation, and 

 one discharging the mner membrane investing the brood of macrogonidia (Bi'aun), x400, 

 65. Same as 63, seen from the edge, X 400. 66. Same, seen in f. v., the cells now slightly 

 emarginate, x400. 67. Same, four hours after the macrogonidia have ceased to move, the 

 marginal cells now drawn out into horns, but not yet having assumed their proper form» 

 and all exhibiting spaces between, not yet having become closely applied to each other, 

 X 400. 68, 69. P. Boryanum : microgonidia treated with tincture of iodine and stJ- 

 phuric acid, showing the vibratile cilia, the slightly retracted contents, and a nucleus, 

 X 500. (Figs. 63-69 after Braun. ) 



PLATE II. (Desmids). 



Figures 1 &/ 5. Closterium Leibleinii (Kg.), x200 : 1. A frond filled with endochrome, 

 and an empty one lying across it (tlie latter shows the central sutiu-e) ; 5. Sporangium lying 

 between the conjugated, and now empty fronds. 2 & 6. Closterium sti'iolatum (Ehr.), 

 X 100 : 2. A frond with endochrome, showing the longitudinal fillets and the single row of 

 large granules; 6. Two empty conjugated fronds,^ showing the stri« and the orbicidar 



