388 STUDIES IN VEGETABLE BIOLOGY. 
has been to cause most of the chlorophyll grains to collect upon the 
lower wall ; but a few are still in the lateral position. 
Fig. 18. Shows negative apostrophe still incomplete after ten days. 
Figs. 19-22. Mesocarpus scalaris. 
Fig. 19. Broadside and profile views of chlorophyll plates. x 140. 
20. Positive apostrophe and positive condensation of the plates, x 140: 
l .a, thirty minutes’, b, fifty minutes’ insolation. 
21. Figures produced by the attraction of parts of the plates to oppo- 
site sides of the cell: a x 450, b x 350. 
22. Shows the effect of fourteen days' darkness (October) upon plates 
which were face-up before confinement: n, the nucleus pushed to 
the side-wall by the advance of the plate thither. x 140. 
Puare XV. 
Figs. 23-26. Senecio vulgaris. 
Fig. 23. a and 5 show the effect of six hours’ sunlight with short intervals 
of shade upon palisade-chlorophyll. 
24. Coalescence in a mesophyll-cell. Same conditions as those of fig. 23. 
x 600. 
25. A mesophyll-cell, showing coalescence in the arms, at coh coalescence 
not yet established. Same conditions as those of fig. 23. — 
26. Expressed chlorophyll figures obtained after several hours’ exposure to 
the sun. x 600. 
Solanum nigrum. 
Fig. 27. Coalescence in the arm of a mesophyll-cell; seven and a half hours’ 
insolation. x 600. 
Vallisneria spiralis. 
Fig. 28. Effects of prolonged sunlight: a, grains become polyhedral by mutual 
pressure; ò, c, e, phases of cohesion and coalescence; d, grains 
cohering with the nucleus. x 600. 
Helianthus annuus. 
Fig. 29. a, a mesophyll-cell showing coalescence; b, ive grains closely packed 
in a cell's arm. (In darkness forty-one hours.) X 600. 
Senecio vulgaris. 
Fig. 30. Expressed chlorophyll figures from a plant kept one week 1n darkness. 
x 600. 
Bryonia dioica. 
Fig. 31. Arm of a mesophyll-cell from a plant shut up nearly four days in the 
dark, with angular chlorophyll grains. x 600. 
