--IN VEGETABLE BIOLOGY. -- 9868 
It was shown in the previous memoir that Lemna trisulca 
is exceptional, inasmuch as in this type the negative apostrophe. 
is almost completed in a very short time, although a few grains 
remain in epistrophe days after. Much the same thing is seen 
in the mesophyll of Circea lutetiana and also in Potamogeton 
erispus. Moreover, after positive apostrophe, epistrophe is only 
very partially induced in darkness with these three. Perhaps 
the peculiarity as affecting Oircea lutetiana may be in part due to 
the small amount of chlorophyll in its mesophyll-cells, and the 
consequently unimpeded progress of the grains towards the side- 
walls. But I am inclined to think that when its tissues are 
exceptionally transparent, although a plant may be a shade-lover, 
yet its protoplasm is toned to higher grades of illumination than 
would be the case were the leaves more opaque. 
It was also shown that the chlorophyll of palisade-tissues is far 
more movable than had hitherto been supposed ; and, moreover, 
that the grains can be made to mass in darkness. I have ob- 
served positive massing in Viola odorata after between three and 
four hours' insolation ; not only are the masses on the side-walls, 
but they may occasionally be seen closely covering the lower wall 
instead of, as is the case in diffused light, presenting in bird's-eye 
view a-sort of tunnel lined all round with chloroplasts. In some 
of the palisade-cells of Convolvulus arvensis, Platystemon califor- 
nicus, and Hydrocotyle vulgaris massing occurred after 4 hours in 
. sunlight ; in Chrysanthemum segetum, Tropeolum majus, and Mat- 
thiola incana after 6 hours; and in some of the large subepidermal 
cells of Hydrocharis Morsus-rane after prolonged insolation. On 
the other hand, it required 3 days’ darkness to effect much altera- 
tion in the position of the chlorophyll of Viola odorata: in dark- 
ness, as well as in sunlight, the grains of this type may sometimes 
be seen massed upon the lower wall (fig. 17). Negative massing 
was also found in Cheiranthus Cheiri after 23 days in the dark, 
in Hydrocharis Morsus-rane after a week, and after varying 
periods of confinement in many others, including Senecio vul- 
garis, Primula vulgaris, Godetia rubicunda, Hibiscus africanus, &c. 
The palisade-chloroplasts of Circea lutetiana were found col- 
lected into masses after confinement for five days, during which 
„Period those of the subjacent mesophyll-cells showed no tendency 
to mass. 
A few words may be here added as to the method of examina- 
tion resorted to in the above and similar cases. I have discarded, 
