448 MR. A. J. EWART ON ASSIMILATORY INHIBITION, 
Cuscuta Cephalanti. 
1. Young pale-yellow seedlings, a few cm. long. Chlorophyll grains faint 
greenish yellow. No evolution of oxygen shown in light. 
2. Young plants, with well-formed thick coils, with plenty of haustoria. 
Colour is brownish yellow. Epidermal cells, starch almost entirely 
absent, chlorophyll grains small and deeply reddish brown, weak 
evolution of oxygen. Cortex, brownish-yellow chlorophyll grains, 
starch abundant, frequently 2 or 3 grains to one chlorophyll body; 
moderately active evolution of oxygen. Inner cortex, chlorophyll 
grains yellowish green, starch as before; evolution of oxygen slightly 
more active than from outer cortex. 
3. Plants over 3 months old. Chlorophyll grains brownish red. For 
most part each has formed a group of starch grains, between which 
the body of the chlorophyll grain is seen only as a reddish-brown 
matrix. In cells quite packed with starch, generally no power of 
assimilation can be detected; but where less starch is present (outer 
parts of older and all parts of younger stems), a weak to moderately 
active evolution of oxygen isshown. Young buds 0'3 em. long, from 
the axils of the scales, contain distinet round small pale yellowish-green 
chlorophyll bodies; but no evolution of oxygen is shown. When 1 cm. 
long or more, the chlorophyll grains are yellowish to greenish brown, 
and show distinct but not strong assimilation. 
C. Cephalanti therefore possesses a distinct power of assimi- 
lation, which eommenees as soon as the chlorophyll grains are 
mature, and continues after all green coloration has been masked 
by the formation of a reddish-brown pigment, which is probably 
a derivative of chlorophyll*. Under favourable conditions the 
bulk of the Cuscuta plants was much greater than that of the 
plants (Convolvulus) on which they were parasitic. 
* In such cells the nucleus may often be seen to be coloured faintly 
brownish whilst the cell is still living, and in dead cells the coloration generally 
deepens. Campbell (‘The Staining of Living Nuclei,” Arbeit, Bot. Inst. 
Tübingen, Bd. ii. 1887) has shown that the living nucleus may be stained by 
certain aniline dyes. The above case is interesting as being an example of a 
normally stained living nucleus, The shape of the nucleus also is often 
peculiar ; it may be acicular, spindle-shaped, or stalked, with a club-shaped 
extremity projecting into the lumina of the cell, and the stalk may be longer 
than the diameter of the cell, in which case it is coiled in one or two turns. 
The nuclei of C. europea rarely show the same peculiarites of form, but are 
generally round or oval and normal in shape. 
