440 MR. A. J. EWART ON ASSIMILATORY INHIBITION. 
Similar results as regards assimilation were obtained with 
freshwater Algs exposed in water kept below 15° C. for 10 hours, 
the sun being slightly clouded during the first five, but unclouded 
during the last five hours. 
Spirogyra; | Many filaments dead, but plenty living and with unbleached 
(Edogonium.| chlorophyll, but no assimilation; none after 2 h. in 
diffuse light, weak in 5 h., and about normal in all living 
filaments next day. 
Mesocarpus. | All cells killed and bleached. After 4h. exposure to sun- 
light plenty of living and normal cells show no assimila- 
tion, and mostly none after 2 h. in diffuse light. Next 
day assimilation is shown by all living cells. 
Similarly with shade-loving land-plants after 12 hours’ expo- 
sure to full sunlight :— 
Dicranum Leaves living and green, but assimilation absent entirely or 
scoparium. from apical part only, and where present weak. After 
2-4 h. in diffuse light, assimilation is active. 
Oxalis Leaflets green and living, but drooping, and in some cases 
Acetosella. slightly wilted. No assimilation shown. After 1-2 h. 
in diffuse light faint, and in 2-3 h. fairly active assimila- 
tion, and the leaflets have re-expanded. Leaflets shaded 
in the drooping position may show a weak assimilation, 
bat none if a reflecting mirror has been placed behind 
them. 
The drooping position assumed by the leaflets of Oxalis is 
simply protective; there is no correlation between the assump- 
tion of the drooping position and the temporary loss of the 
power of assimilation. Preparations made at night from the 
leaves of Ozalis when in the drooping nyctitropic position show 
a normally active power of assimilation, and the same is the 
case with leaflets of Mimosa. The movements performed in 
assuming the nocturnal nyctitropic position of certain “sleep” 
plants are not accompanied by any corresponding internal 
changes or alterations in the power of assimilation. In this 
respect the sleep of plants is more external and apparent than 
internal and real. 
With sufficiently prolonged exposure stoppages of the power 
of assimilation can be caused in the leaves of Phanerogamic trees 
and shrubs. 
