MR. A. J. EWART ON ASSIMILATORY INHIBITION. 447 
are left in situ on the turf from which they are growing, all 
parts above ground except the Euphrasia-stems being removed, 
and the turf kept moist during the exposure, the conditions are 
more normal and the plants more resistant; but after a day’s 
exposure to full sunlight, the fully exposed leaves, though green, 
living, and apparently normal, show none or only a weak power 
of assimilation. 
All cells, whether from parasitic or non-parasitic plants, which 
contain normal chlorophyll grains possess the power of assimi- 
lation, and the intensity of the assimilation bears a direct ratio 
to the amount of chlorophyll present. The amount of assimi- 
lation is of course dependent upon the intensity and duration 
of the illumination, but is also owing to the fact that the rate at 
which the assimilatory products are removed exercises an im- 
portant influence upon the power of assimilation, ultimately 
dependent upon the special internal structure and vital pecu- 
liarities of each individual plant, which are in no two cases 
precisely similar. 
Even in plants in which neither the colour nor the form of 
the chlorophyll grains is normal, a marked power of assimilation 
may still be present. Thus Temme * has extracted chlorophyll 
from Cuscuta europea, though it is only present in relatively 
small amount. By passing an assimilatory mixture of H and CO, 
over the plants when exposed to sunlight, and using the oxidation 
. of phosphorus as a test for the presence of oxygen, he succeeded 
in detecting an evolution of oxygen from them. The experi- 
ments are, however, not conclusive as to whether the oxygen 
evolved is produced on exposure to light or was previously 
present in the tissues of the plant. The green-colouring material, 
according to Temme, exists partly in the uniformly green plasma, 
or in separate plasma masses or in grains, this last form being 
only found in the flower-heads. Detailed and conclusive obser- 
vations can be made only by means of the Bacterium method, 
the following being the results thus obtained with Cuscuta 
Cephalanti :— 
* Temme, “Ueber das Chlorophyll und die Assimilation der Cuscuta 
europea,” in Ber d. D. Bot. Gesell. 1883, Bd. i. p. 485. 
