1922] RANDOLPH—MAIZE 353 
The cells of the yellowish green plants show a series of stages in 
the development of chloroplasts from minute proplastids which are 
similar in all respects to the stages in the green plants, with the 
exception of the maximum size and depth of color attained. The 
proplastids increase in size until many of them have become well 
differentiated plastids with a diameter of 4.0-5.5 pw (figs. 33-41), 
whereas the plastids in normal green plants have a diameter of 
7-8 wu; very exceptionally the latter size may be attained (fig. 41). 
The plastids in the pale areas of the seedling leaves are fewer in 
number, and the proplastids are more numerous than in the 
corresponding cells of a green plant (fig. 39). A study of the living 
cells shows a variable behavior as regards the elaboration of 
chlorophyll in the young seedling leaves. In the mesophyll cells 
most of the plastids become faintly green as soon as they become 
partially mature (fig. 39), while in cells near the vascular bundles 
plastids are often observed in which the color has become nearly 
as deep as in a normal mature chloroplast (fig. 41). In cells 
somewhat removed from the bundles all gradations between the 
lighter and darker shades are seen (fig. 40). In addition to the 
uniformly colored plastids, there are others which show an uneven 
outline and an irregular distribution of the pigment within them. 
For example, the color is often confined to one or two regions 
within the plastid, the limits of these regions in some cases being 
clearly marked and in others very vague (fig. 39). Such appear- 
ances strongly suggest degeneration or other disturbances of a 
serious nature. Not only young cells, but cells which are com- 
pletely matured, contain proplastids in various stages of enlarge- 
ment. 
The plastids are much more fully developed in the yellowish 
green plants than in the albino seedlings of the “‘ Mendelian white” 
strain, but a sufficient amount of chlorophyll for continued growth 
fails to be developed, and the plants die in the seedling stage. 
They may become slightly larger, however, than the white seedlings 
of the Mendelian strain. In the yellowish green plants there is 
little correlation between the degree of development reached by 
the plastids and the amount of chlorophyll elaborated. There 
are abundant well differentiated plastids present but only a rela- 
