372 MR. S. LE M. MOORE'S STUDIES 
has apparently set in. The mesophyll is, however, the best tissue 
for the present purpose. At fig. 24 is shown a chlorophyll mass 
whereof nearly one half was composed of grains forming by their 
eoalescence an irregularly outlined figure, the remaining grains 
merely cohering together. A view of an entire mesophyll-cell 
is given in fig. 25; this shows grains in several places so com- 
pletely coalesced, that it was impossible with the best focussing to 
resolve the mass into its constituent portions—at another spot 
(marked coh) perhaps cohering, though possibly only closely 
massed; and at one point in simple apostrophe. The figures 
formed by the coalesced chlorophyll grains are very various; 
indeed, they depend upon the form and extent of the cell's arms, 
in which they lie pressed together so tightly that the original, 
lines of separation have vanished. As another instance of this 
may be cited the mesophyll of Solanum nigrum (fig. 27) after seven 
and a half hours’ insolation. In this figure the grains in the cell's 
arm have to all appearance coalesced, while those in the imme- 
diate neighbourhood were in cohesion. Similar facts were ob- 
served in a number of types, among others Reseda odorata and 
Circea lutetiana upon seven hours’, and Nigella damascena, 
Mathiola incana, and Tropeolum majus after six hours’ inso- 
lation. 
It is necessary to add that great caution is required before 
determining that the chlorophyll grains have really coalesced, as 
in many cases of apparent coalescence more careful examination 
teaches that cohesion, or sometimes mere massing, is alone in 
question : this is especially frequent when the presumed coalesced 
mass stands side up to the observer, since a number of grains 
closely packed one behind the other may produce an impression 
of solidarity which, as surface-views may show, is far from being 
the actual state of affairs. A satisfactory proof of coalescence is 
furnished by what it is proposed to call “ chlorophyll figures: " 
these are obtained by teasing out in water small pieces or sections 
of leaves previously exposed to sunlight for several hours, under 
which circumstances among the numerous single chloroplasts 
may here and there be found floating masses of chlorophyll much 
larger than individual grains, and sometimes still retaining, in 
spite of the action of the water, the form impressed upon them by 
the limits of the space within which they were packed. Such is 
the source of figs. 26 a-c, taken from a leaf of Senecio vulgaris 
insolated for seven and a half hours. It must be confessed, 
