556 DR. A. J. EWART ON ASSIMILATORY INHIBITION. 
Pinus Pinea,.—Seedlings developed in darkness at 20? C. to 22° C. 
(a) Hypocotyl 4 cm., leaves 2°5 to 3 em. long. Chlorophyll grains green 
but with slightly yellowish tinge. Oil drops in cell protoplasm. Pre- 
parations readily injured. Longitudinal sections through subdermal layers 
are best and show quite distinct but not strong power of assimilation. 
(b) Leaves green, about 4 em. long, bases pale. Chloroplastids have slight 
yellowish tinge and are paler than the same grains developed in light. 
Weak but distinct evolution of oxygen. 
(c) Older plants. Cotyledonary leaves 6 cm. long, green but basal parts 
pale, protoplasm starved and attenuated. Apical tuft 2 em. long ; leaves— 
apical part pale green, basal part white. No evolution of O in light from 
either primary or secondary leaves. Brought into light the plants remain 
living for a few days and then mostly die without showing any return of 
the power of assimilation. A few remain living, the chlorophyll grains 
finally become deeper green and slightly larger, and show in 2 days a 
quite distinct power of assimilation, which in 3-4 days is fairly active. 
The chloroplastids of Pinus Pinea, therefore, when developed 
in darkness are, though green, partially etiolated, and have a 
distinct but not strong power of assimilation, which later is 
lost. 
For the experiments upon assimilation in etiolated plants 
seedlings from plants with large seeds were at first used. The 
following are the results :— 
Helianthus annuus.—(1) Young plants: cotyledons deep yellow, cells filled 
with starch. No evolution of O perceptible. (2) Older plants, 20 em. 
high ; cotyledons 1:3 cm. long by ‘8 em. broad, dark yellow with but little 
starch ; chloroplastids fairly large, distinct, and yellow; moderately active 
evolution of O. (3) Still older plants 20 cm. high ; stem and young leaves 
quite pale and colourless; no evolution of O. Cotyledon 1:5 by ‘9; chlo- 
roplastids fairly large, quite yellow ; protoplasm clear and transparent ; 
distinct but only weak evolution of O. (4) 5 days longer in darkness. 
No further growth. Cotyledons very slightly paler and chloroplastids 
slightly smaller. No evolution of O perceptible. In light the intact 
cotyledons and in many cases the attached lower halves of the cotyledons 
used for sections, if the cut surface is covered with vaseline, remain living, 
show in 2 to 3 days a faint evolution of O, and begin to turn green. 
Cucurbita Pepo.-—(1) Young plants : cotyledons deep yellow, cells filled with 
starch ; no evolution of O perceptible. (2) 8 days later, deeper yellow, 
starch less in quantity; weak but distinct evolution of O. (3) 5 days 
later, very little starch; cotyledons dark yellow; chloroplastids fairly large, 
distinct, and quite yellow. Plant 20 em. high, with cotyledons 2 cm. by 
1, showing moderately active power of assimilation. (4) 5 days later, 
plant 24 cm., cotyledons 39:5 em. by 1°5; Ist foliage leaf, lamina ‘5 by 
`8 cm., 2nd and stem 1-5 em. long. Ist young foliage leaf is quite pale 
or faintly yellow and shows no evolution of O.. Cotyledons, chloroplas- 
tids yellow, and somewhat smaller cells slightly starved ; distinct but weak 
evolution of O. (5) 5 days later. Plants no larger, still more starved. 
