12 
PLANT MORPHOLOGY. 
found in dried material in a more or less altered con- 
dition. 
The leucoplastids were first carefully studied by 
Schimper. Their chief function is that of building 
up reserve starches, and they may be best studied in 
the common potato tuber, rhizome of iris and the 
pseudo-bulbs of Phajus grandijlorus. 
The chloroplastids occur in all the green parts of 
plants. They vary from 3 to 11 /j. in diameter and 
are more or less spherical or lenticular in shape, 
except in some of the lower algse. They are found in 
greater abundance in the cells near the upper surface 
of the leaf than upon the under surface, the propor- 
tion being about five to one. These grains upon close 
examination are found to consist of (1) a colorless 
stroma, or liquid, in which are imbedded (2) green 
granules ; (3) colorless granules ; (4) protein masses ; 
(5) starch grains; and finally (6) a membrane sur- 
rounding the whole. The green granules are looked 
upon as the C0 2 assimilation 1 bodies ; the colorless 
grains are supposed to assist in the storing of starch 
or in the production of diastase, the conditions for 
these processes being directly opposite, i.e., when C0 2 
assimilation is active, starch is stored, and when this 
process is not going on, as at night, diastase is pro- 
duced and the starch is dissolved. The protein grains 
may be in the nature of a reserve material of the 
plastid and are also formed as a result of C0 2 assimi- 
lation. 
CHANGES IN THE COLOR OF C H LOROPLASTI DS. 
When the organized contents of the cell lose their 
functions, the membranes of the chloroplastids are 
1 The process of C0 2 assimilation consists in the taking up of 
the inorganic compounds C0 2 and H 2 0 and converting them into 
starch, the first visible product of constructive metabolism, oxy- 
gen being given off at the same time. 
