IN VEGETABLE BIOLOGY. 373 
however, that the number of these escaped masses is not so great 
as might be expected: this is probably due to difficulty in dis- 
lodging them from the cells without injury. 
If a leaf of Vallisneria spiralis be cut off and set in water in a 
shallow vessel exposed to bright' sunlight, the protoplasm both 
of the superficial and deep cells soon begins to rotate, the chlo- 
rophyll being carried along with the stream. This movement 
will continue for some time; but in long-continued sunlight it 
eventually comes to an end, a prelude to the destruction of the 
protoplasm whereof this is the first visible sign. In cells with 
this light-stiffened protoplasm it is usual to find the chlorophyll 
massed upon any wall, frequently round the nucleus; and careful 
examination will show that the originally round grains have become 
polyhedral by mutual pressure (fig. 28a). By prolonging the 
insolation—any recovery in diffused light (supposing the proto- 
plasm to be capable of such) being prevented by setting the leaf in 
darkness overnight and retaining it there ready for removal to sun- 
light on the morrow—the massed grains can be seen first to cohere, 
and ultimately in some cases to coalesce into figures of variable 
shape, occasionally forming a beautiful lattice-work extending 
over a small part or almost the whole of the cell (figs. 28 b-e). 
Destruction of the protoplasm is accompanied *—never, I believe, 
preceded—by discoloration of the chlorophyll, which still retains, 
for some time at least, the forms impressed upon it by virtue of 
the coalescence of its grains. The ultimate fate of the coalesced 
masses was not ascertained. mE 
Although less expeditious, it is easier to study this pheno- 
menon from the negative side, because the requisite conditions, 
obtained with so much difficulty when the agency of sunlight is 
invoked, can always be readily commanded. Helianthus annuus 
is a convenient type, though almost any plant? will answer the 
purpose. A small mesophyll cell of this species from a plant 
confined to darkness for forty-one hours is represented at fig. 29 a : 
it shows the chlorophyll coalesced into four masses 1n the cell’s 
arms ; two, being broadside on, have stood the test of the fullest 
examination; in the other two, which are somewhat in profile, 
there seems no doubt of coalescence, although faint indications 
* Perhaps followed ; for it is difficult to say exactly when the protoplasm 
actually dies, . 
t A sun-lover should be selected, because negative apostrophe and massing 
are readily induced in such. 
