MR. A. J. EWART ON ASSIMILATORY INHIBITION. 449 
Cuscuta europea. 
(4) Young plants 30 to 40 cm. long. Apex is greenish yellow; but 
chlorophyll grains almost colourless, the apparent deepness of the 
coloration being due to the transparency of the young tissues. Starch 
grains few or none. No assimilation. Ist internode: pale greenish 
yellow; chlorophyll grains faint yellow, more starch; very weak 
evolution of oxygen. 2nd internode: paler in colour, but chlorophyll 
grains more deeply greenish yellow; starch abundant; moderately 
active evolution of oxygen. Brd internode: red, due to dye in sap of 
epidermal celis; rest as in 2nd internode. 4th internode: coiled 
several times round nettle-stem and with plenty of haustoria; starch 
very abundant, but otherwise as in 2nd internode. The colour of the 
chlorophyll grains is not very deep, but they are distinet and separate 
when no, or only one, starch grain is present. When several starch 
grains are formed, the outline of the chlorophyll grain is generally lost, 
the group of starch grains appearing simply to be united by a yellowish 
matrix in which they are imbedded. 
(b) Stems from adult flowering plants. In outer cortex, less starch, fewer 
chlorophyll grains, and weak evolution of oxygen. In inner cortex, 
starch and chlorophyll grains more abundant, and fairly active 
evolution of oxygen. From cells quite packed with starch, no evolution 
of oxygen is perceptible. The chlorophyll grains may fuse to form an 
irregular coloured amyliferous mass, and are rarely spindle-shaped 
instead of round or oval. 
(c) Inflorescences. In the outer tissue forming the walls of the anthers 
normal small green chlorophyll grains are present, and a weak to 
moderately active assimilation 1s shown until after dehiscence. In the 
large cells of the adherent calyx the chlorophyll grains are few in 
number, but moderately large and distinctly green, and a weak but | 
distinet evolution of oxygen is shown. The central earpellary portion | 
is much greener. The chlorophyll grains have a tendency to fuse to 
form large green irregular masses with or without stareh grains. | 
More than one such mass may be present in the cell, but the rest of the 
plasma is colourless. Plenty of cells contain quite normal, but | 
somewhat pale green chlorophyll grains. Fairly active evolution of 
oxygen, whether the grains are single or fused, and with or without 
starch. From some cells quite packed with starch, the evolution of 
oxygen is weak or imperceptible. | 
The power of assimilation exhibited by the chlorophyllaceous 
stems of C. europea is weaker than in similar green stems of 
Convolvulus, but not more so than would be expected from the 
less amount and weak intensity of coloration of the chlorophyll 
bodies. In the chlorophyllaceous parts of the flower the power 
of assimilation is quite as active, if not more active, than is 
generally the case in such parts. Wiesner * has shown that in 
Neottia Nia.s-avis and in the Orobanchee distinct chlorophyll 
* J. Wiesner, “Untersuchungen über die Farbstoff einiger für chloro- 
phyllfrei gehaltenen Phanerogamen,” in Pringsh. Jahrb. Bd. viii. 1872, p. 575. 
