| DR. A. J. EWART ON ASSIMILATORY INHIBITION. 563 
Daucus Carota.—(a) Leaf 12 cm., laminal portion 1 cm., yellow not very 
deep. Entire thin leaflets examined, in apical parts colour is deeper, and 
here distinct but extremely weak evolution of O is shown, in rest imper- 
ceptible. (b) Leaves older and 15 cm. long, are yellow, but show no 
evolution of O. 
P Brassica Napus.— Leaf 23 em., terminal leaflet 3:5 by 1 em., largest lateral 
leaflet 2 by 1 cm. Chloroplastids pale yellow. Colour deepest in the 
imperfectly differentiated palisade parenchyma layers. Here a distinct 
but rather weak evolution of O is shown (stronger than in any of the 
other foliage-leaves examined). From the other etiolated assimilatory 
cells and tissues a distinct but much weaker evolution of O. 
Apium graveolens.—(a) Young leaf 5 em., leaflets pale yellow ; no assimila- 
tion perceptible. (b) Leaf 8 cm., in parts yellow colour is deeper; here 
a just perceptible trace of assimilation is shown, in rest none. 
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a. Open bent glass tube painted black 
inside and out. 
b. Layer of coarse emery powder. 
c. Cork, through which the Chara 
stems pass. 
d. Painted andopaque glass cylinder, 
in the figure drawn as if trans- 
parent. 
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