DR. A. J. EWART ON ASSIMILATORY INHIBITION. 559 
dilute acid to obtain chlorophyllan, or with very dilute alkali to 
obtain alka-chlorophyll, gave in all cases negative results. If 
after the crushed etiolated cotyledons have been treated with 
dilute alkali, ether is added, the latter becomes pure yellow and 
leaves finally a perfectly colourless residue, thus proving the 
absence of all chlorophyll. 
It is therefore in this case certain that etiolin can act as an 
assimilatory pigment, the assimilation being never more than 
moderately active, because the colour of the chloroplastids is 
much paler than when they are green, the etiolin being less 
abundant, and absorbing less light than chlorophyll does. 
The quite young cotyledons are unable to assimilate owing to 
the fact that the cells are packed with starch and that the 
etiolated chlorophyll grains are not as yet fully developed. If 
the cotyledons are allowed to develop in light and turn green, 
they show a distinct power of assimilation at a much earlier 
stage and whilst much more starch is still present than when 
grown in darkness. In seedlings kept for a long time in darkness, 
the etiolated cotyledons finally lose the power of assimilation. 
This is in such cases partially a phenomenon of starvation, the 
etiolated chloroplastids becoming slightly smaller and paler, but 
is also due to the fact that chloroplastids when kept under con- 
ditions in which they are of necessity functionless (darkness, 
absence of CO,) finally lose the power of assimilation. The 
longer the seedlings are kept in darkness or the older the 
individual leaves may be, the longer they take to turn green and 
regain their normal assimilatory powers when brought into the 
light. In seedlings this is undoubtedly partly due to the influ- 
ence exercised upon the chloroplastids by the starvation to which 
they are finally subjected. 
If seedlings of Phaseolus multiflorus are grown in darkness 
until further growth ceases, the largest plants have stems nearly 
1 metre long, the basal simple leaves being 2 by 3 cm. and the 
petioles 5 to 7 cm., and 4 to 6 or more compound leaves, the 
largest lamina of which is not longer than 1 cm., being present. 
If such plants are brought into light, in some cases all the leaves 
die and the pale stem may remain living for as long as 2 weeks, 
but has no strength to bud out new leaves and finally dies. In 
some of the upper leaves the terminal leaflet remains yellow for 
as long as 8 weeks and then dies, the basal pair beginning to 
turn green in 1 week and in 2 are quite green. Certain of the 
