Igto]_ - LUTMAN—CELL STRUCTURE OF CLOSTERIUM 255 
EXPLANATION OF PLATES XVII AND XVIII ~ 
MacniricaTion.—Figs. 1, 2, 5, 6, 7, about Xgoo; all the others, about X 1250. 
Fic. 1.—C. Ehrenbergti; longitudinal section; on the left the section is 
through one of the ridges; on the right it is through one of the furrows; , nucleus; 
P, pyrenoids; s, stroma starch. 
Fic. 2—C. Ehrenbergii,; cross section. 
"IG. 3.—C. Ehrenbergii; cross section near one end, _ showing star-shaped 
chromatophore. 
Fic. 4.—C. moniliferum,; shaded portion is the central part of the chromato- 
phore. 
Fic. 5.—-C. moniliferum; schematic cross section through the nucleus (7); 
&¢, granular cytoplasm. 
Fic. 6.--C. moniliferum; cross section about half- -way to the tip. 
Fic. 7.—C. moniliferum; cross section nearer the tip. 
Fics. 8-26.—C. Ehrenbergii; details of starch and pyrenoids. 
Fic. 8.—Stroma starch. 
FiG. 9.—Pyrenoid showing internal markings; a, in section; }, surface view 
of the starch mass 
Fic. ro. —Pyrenisd showing internal markings; a, section of starch showing 
top of pyrenoid; 8, section of starch and pyrenoid; c, section showing lower part 
of the starch. 
Fic. 11.—Pyrenoid; a, section; 6, top surface of starch mass; c, bottom of 
me. - 
Fics. 12, 1 3.-—Pyrenoids; a, surface view of starch; 5, section of pyrenoid. 
Fic. 14.—Pyrenoid; a, section; b, surface view of starch; c, view of the 
Starch at deeper level. 
Fic. 15.—Pyrenoid; a, surface of starch; 6, section of pyrenoid. 
Fics. 16-22. <b precipi showing pieces cut off. 
Fic. 23.—-Pyrenoid with large vacuole. 
ie 24.—Pyrenoid after Closterium has been kept i in the darkness for three 
Fries 25, 26.—-Pyrenoids showing peculiar disks into which the pyrenoid 
body has broken u up. 
Fic. 27.—Pyrenoid as ordinarily figured in division. 
Fic. 28.— Nucleus of C. moniliferum. 
Fic. 29.—Nucleus of C. Ehrenbergii. 
