IN VEGETABLE BIOLOGY. 209 
negative apostrophe ; with ordinary aerophytes this will result 
in low light, under which circumstances apostrophe is set up in 
periods approximately, though not quite, equal to those necessary 
for its production in darkness. I have witnessed this with Funaria 
hygrometrica, seedlings of Eschscholtzia californica, and involucral 
scales of garden Chrysanthemum and Senecio vulgaris, as well as 
leaf-sheaths of Poa annua; and as no exception has been discovered, 
this is probably a rule of universal application to plants of this 
kind. ` 
Massing of the grains on prolonged withdrawal of light has 
already been mentioned as occurring in ordinary aerophytes, 
Even Funaria hygrometrica may sometimes, though very rarely, 
show it, the grains collecting usually upon the fore or the aft wall, 
orboth. Fig. 4 (Pl. VII.) is taken from a plant kept a fortnight in 
very low light. In the leaf-sheaths of Poa annua kept in darkness 
for twenty-four hours, fore-and-aft massing may sometimes be 
observed ; but when it does occur, massing is usually in the form 
represented in figs. 5 a and b, the nucleus being the focus round 
which most of tbe grains are distributed. Nor do aquatic types 
yield negative results, for if Lemna trisulca plants be examined 
after about a month’s incarceration, the grains, greatly reduced 
in size and discoloured, of the marginal cells will be found to a 
large extent collected in little heaps in their angles. Moreover, 
if small pieces containing about half-a-dozen internodes of Elodea 
be set in darkness, the greater number of the grains may after 
some days be disposed upon the walls, either in fore-and-aft 
arrangement (fig. 6 a), in the corners (6 5), or to a greater or less 
extent upon the nucleus (6c). So, too, with Callitriche verna: 
fig. 7 a shows most of the grains of a cell in simple apostrophe 
after ten days’ darkness; figs. 7 b and c represent the effects of 
ten days in the dark upon cells nearer the apex of the leaf (where 
apostrophe more quickly betrays itself), in which the grains are 
reduced in size and have massed, this time not in the angles, and 
not always upon one of the lateral walls*. It would seem, then, 
that massing is of frequent occurrence, not only among aero- 
phytes but also in aquatic types. 
But this is not all. Numerous experiments, especially those of 
Stahl, have shown that the grains in the palisade tissue of the 
leaves of phanerogams are ordinarily very little movable on inso- 
* In his second memoir Böhm notices massing of the chlorophyll of Sedum 
spurium in the dark. 
