1911] LUTMAN—CLOSTERIUM 429 
46. West, G. S., On variation in the Desmideae and its bearing on their 
classification. Jour. Linn. Soc. Bot. 34:376. 1899. 
47. Wotre, J. J., Cytological studies on Nemalion. Annals of Botany 18: 
607-630. 1904. 
48. Zacuartas, E., Ueber den Nucleolus. Bot. Zeit. 43:257-265, 273-283, 
289-296. 1885. 
EXPLANATION OF PLATES XXII AND XXIII 
All figures were drawn with the aid of a camera lucida; the majority of 
them with the Leitz }, achromatic objectives and eyepieces, and the others 
with the Zeiss 3 mm. apochromatics and compensating oculars. The approxi- 
mate magnification is indicated after each figure. Figs. 1-13 are from whole 
mounts in glycerin, and are diagrammatic in that they do not show the slight 
shrinkage of cell contents due to fixation and transfer to glycerin. The other 
figures are all from sections 5-10 in thickness, stained with the triple stain, 
€xcept fig. 29, which is from a slide stained with iron-hematoxylin. 
C. Ehrenbergit 
Fic. 1—Chromatophore just beginning to show constrictions; 300. 
Fic. 2.—Nucleus in metaphase; transverse cell wall beginning; X 300. 
Fic. 3.—Transverse cell wall nearly complete; nuclei not showing; X 300 
Fic. 4.—Transverse wall complete; nuclei moving back to their new 
Position; 300. ; 
Fic. 5—New ends beginning to round off; nuclei at constriction; X 300. 
Fic. 6.—New end still further rounded; X 300. 
Fic. 7.—Position of nucleus between the ridges of the chromatophore as 
Seen from the convex side; > 300. 
Fic. 8.—Individual with asymmetrical halves; the chromatophore not 
a completely divided; the new tip beginning to assume its pointed shape; 
300. 
C. moniliferum 
: F IG. 9.—First appearance of constriction in the chromatophore; pyrenoids 
dividing 50. 
Fic. 10.—Individual with two halves just ready to separate; X 550. 
Fics. 11-13.—Various stages in the change of form of the new halves; 
8. 11 showing pyrenoids dividing; fig. 11, X 550; figs. 12, 13, 475. 
, 
C. Ehrenbergii ; 
: IGS. 14, 15.—The resting nucleus in side view; X 1800. 
1G. 16.—Resting nucleus in end view; X 1800. 
