374 BOTANICAL GAZETTE i 
PLATE XII 
Mendelian white seedling 
Amount of green color present in chloroplasts after they have reached a 
size of 2.5 wu indicated by depth of shading; stages represented in this series 
taken from a 3-inch seedling about six days after germination 
Fics. to—12.—Successively older stages in development at proplastids in 
undifferentiated meristematic tissue; cells in median section; fig. 10, pro- 
meristematic cell from stem tip; fig. 11, from tip of leaf bud recently form 
‘from apex of stem; fig. 12, from tip of 18 mm. embryonic leaf. 
Fics. 13-16.—From different regions of 35 mm. leaf just before emerging 
from enveloping leaves; fig. 13, undifferentiated cell near tip (note abnormal 
appearance of some of proplastids); irregular shape and presence of darker 
regions within proplastids characteristic of certain ones; figs. 14,15, cells 
3-5 mm. from tip; fig. 14, green color entirely absent in all proplastids; fig. 15, 
faint greenish color in one proplastid; others show conditions suggesting 
degeneration; fig. 16, typical mesophyll cell of seedling leaf; slight trace of 
yellowish green color in some of proplastids; others almost colorless or con- 
taining irregular opaque masses. 
Fies. 17-19.—Cells from tip of dulelding seedling leaf. 
Fic. 17.—Undifferentiated cell at tip of leaf; ase proplastids faintly 
green 
Fic. 18.—Cell 3 mm. from tip; larger proplastids (plastids) clearly green. 
Fic. 19.—Mesophyll cell 4.5 mm. from tip; plastids bright green. 
PLATE XIII 
Mendelian virescent 
Depth of shading indicates intensity of green color in later stages of plastid 
development; material of same age as in the case of Mendelian white. 
Fics. 20-23.—From promeristematic = embryonic leaf tissue corre- 
oo to PPE sg stages in green plan 
~26, 32.—From meristematic <0 ae regions of suCc- — 
cn “older tar ee figs. 24-26, before exposure to sunlight; fig. 32, after 
re to sunlight 
Fros. srag Calle from pale green area of seedling leaf. 
Fic. 27.—Mesophyll cell between vascular bundles. 
Fic. 28.—Mesophyll cell nearer vascular bundle. 
Fic. 29.—Cell lying next to vascular bundle. 
Fics. 30-32.—From transition region between pale green and green areas of 
& lea 
Fic. 30. _Mesopbyil cell from slightly green region. 
Fic. 31.—From deeper green region. 
Fic. 32.—Cell from apex of green leaf. 
