352 BOTANICAL GAZETTE [MAY 
other hand, the mesophyll tissue fails to become green as rapidly 
as the tissue near the tip, and the cells between the bundles are 
found to contain only partly developed proplastids (fig. 27). Cells 
nearer the vascular bundles contain larger plastids with more 
chlorophyll (fig. 28), while in cells adjoining the bundles the plastids 
have reached nearly the maximum size and color (fig. 29). In 
somewhat older leaf tissue which is gradually becoming green there 
is a corresponding increase in the size of the proplastids (figs. 30-32), 
and the resulting plastids eventually become fully green (fig. 32). 
Here, then, is a case in which the usual formation of chloroplasts 
with their pigment seems to be merely delayed, but, unlike the 
“Mendelian white” seedlings, development continues until the 
whole plant becomes fully green. 
MATERNAL INHERITANCE STRAIN 
In this strain there are plants of three kinds. Some are entirely 
green and others are uniformly yellowish green; a third class is made 
up of plants which show longitudinal stripes of the two colors. 
The number and character of such stripes are extremely variable. 
Some plants are distinguishable from normal green plants only 
by the presence of one or two stripes, which may be of any width, 
and which may be of a color only slightly lighter than normal 
green. On the other hand, the appearance of some plants is 
rendered most striking by a large number of stripes, which, although 
their yellowish green color varies in depth to a certain degree, are 
never white. Frequently a plant may be divided sharply and 
almost equally throughout its entire length into green and yellowish . 
green halves. Again, plants are observed which are completely 
yellowish green, except for one or two fully green stripes. The 
light stripes, whatever the intensity of their color, are not always 
continuous from the base to the tip of the leaf. In such cases 
they may end more or less abruptly at any point in the leaf, or may 
begin at any point above the base and terminate anywhere between © 
this point and the tip. 
CYTOLOGICAL FEATURES.—With regard to the green plants, 
careful cytological examination has failed to reveal any differences 
between their cells and those of green plants of unaffected strains. 
