MR. A. J. EWART ON ASSIMILATORY INHIBITION. 437 
starch is still present in the cells immediately around the vaseular 
bundles, but the grains are more or less eorroded and lessened in 
number. Here no evolution of oxygen is shown, but in some of 
the outer parts of the stem a very weak power of assimilation 
can be detected. After longer exposure all the green parts, 
including the leaves, lose the power of assimilation, and the 
plants finally die without any further marked decrease in the 
amount of starch present taking place. 
The most effective mode of removing the starch, which shall 
at the same time cause the least possible injurious influence, is to 
keep the plant at a fairly high temperature exposed to extremely 
weak diffuse daylight in an abundant and frequently-renewed 
supply of moist air. After being under such conditions for 
3 weeks, or in darkness for 2 weeks at 30° C., the plants are 
quite healthy, starch has entirely disappeared, the chlorophyll 
grains of the stem are quite normal, round, green, and show, if 
examined after a few hours’ exposure to light, a moderately 
active evolution of oxygen, which is normal for the amount of 
chlorophyll present. 
If the stems are examined after a day or two in darkness, the 
starch grains show as yet no signs of dissolution, and the amount 
of sugar present in the cells must be very small, but no power 
of assimilation is shown. The stoppage of assimilation in these 
leucoplastic chlorophyll grains is due simply to the accumulation 
of starch ; they retain a potential power of assimilation which is 
capable of being exercised as soon as the inhibitory influence 
exercised by the deposited starch is removed. 
In all the cases in which Dehnecke concluded that non- 
assimilatory chlorophyll grains having solely the function of 
amyloplasts were present (pith of Phaseolus and Pisum, chloro- 
phyllaceous cotyledons, &c.), it is only when the chlorophyll 
grain is overloaded with starch that any stoppage of the power 
of assimilation takes place. He cites Hanstein’s observations 
upon the amyliferous chlorophyll grains of the medullary cells 
of Chara, and Sachs upon the chlorophyll “ Bläschen ” in the 
flesh of fruits as proving that the chlorophyll grains in these 
cases also are non-assimilatory. The medullary cells of Chara 
have, however, been shown (pp. 417, 439) to possess a power of 
active assimilation. If tangential sections from the young green 
fruits of Pyrus baccata and P. Torringo—through the outside 
layers in which the chlorophyll grains are abundant, green, and 
pormal—are examined, they are found to show a distinct though 
