1921] SHOW ALTER—CHROMOSOMES 249 
4. The plants received from Ithaca and Copenhagen show the 
same number and size relations of the chromosomes as do the 
Wisconsin plants. 
I wish to acknowledge my indebtedness and gratitude to 
Professor C. E. ALLEN, at whose suggestion and under whose 
direction this study has been made. 
UNIVERSITY OF WISCONSIN 
EXPLANATION OF PLATES IV, V 
All drawings were made with the aid of a camera lucida at a magnification 
of about 3800, using a Zeiss 2mm. apochromatic objective N. A. 1.40 and 
compensating ocular no. 18 with a tube length of 160 mm. 
IGS. 1-11.—Equatorial plate stages in polar view (some slightly eae 
except fig. 11 and one cell in fig. 8, which are in lateral view; symbol followi 
number indicates sex in each case; fig. 1 from cell of dorsal surface layer near 
apical cell; figs. 3-6 from cells of ventral surface layer; in fig. 4 one chromo- 
some at left upper focus cut in sectioning; figs. 7, 10, and 11 from cells of 
interior of thallus; fig. 8, group of six cells in antherid; fig. 9, cell of young 
scale. 
Fic. 12.—Anaphase in cell of air chamber wall, small chromosome being 
visible in upper group o: 
IG. 13.—Early m ehipliase in cell of ventral surface layer, in slightly 
oblique (nearly polar) view; one chromosome, except tip of one end, in adjacent 
section shown in fig. 13a. 
IGS. 14, 14a.—Early hotaphases in cell of interior of thallus, cut in section- 
ing; mer Rae not all distinctly recognizable. 
Fic. 15.—Early metaphase in cell of scale, showing small chromosome 
already divided, other chromosomes not individually distinguishable. 
Fic. 16.—Early anaphase in cell at juncture of scale and main body of 
IGS. 17, 18.—Anaphase daughter groups in successive sections of same 
cell, seventeen in polar ven, eighteen in equatorial view; cell in floor of young 
air chamber. 
1G. 19.—Early anaphase in cell of ventral surface layer; small chromo- 
some not yet divided. 
