IN VEGETABLE BIOLOGY. 355 
Selaginella Martensit is a shade-lover, consequently we should 
expect that if any change be caused in its chlorophyll bodies by 
withdrawal of light, such would not be apparent until after the 
lapse of some time, and this is indeed the case. Ina healthy 
plant it is not until three or four weeks that the effect of darkness 
is perceived. Fig. 9 represents a chlorophyll body, still saddle- 
shaped, after a month and four days in the dark; its position is 
one of semi-apostrophe, two fine bands of colourless plasma 
connecting it with the wall-applied limiting layer of protoplasm *. 
But in leaves exposed to darkness for nine weeks greater changes 
are visible. We may now see the chlorophyll body, much re- 
duced in size, marked by great irregularity of outline, and usually 
consisting of a narrow isthmus connecting two portions of chloro- 
phyll (figs. 10 a, c, d, f). In some cells the threatened fragmen- 
tation (** negative" fragmentation) has actually ensued (figs. 10 
e, f, h,i). Fig. 10 g shows a semilunar chlorophyll-body, the outer 
border of which was near to a side wall, and the position of the 
body represented by fig. 105 plainly hints at apostrophe; but 
this position is not generally assumed even after nine weeks. 
This is, perhaps, no cause for surprise, inasmuch as fragmentation 
in sunlight has been shown to precede apostrophe. 
In very young leaves a faint tinge of chlorophyll may be 
observed over the whole or a part only of the cell’s lumen; it 
appears to be always one mass. The cells of the lower epidermis 
enlarge more rapidly than the chlorophyll body, the latter soon 
taking the form of a band stretching across the lumen, or of a 
rim at its side. This applies also to the elongated cells of the 
upper epidermis; the chlorophyll bodies of its isodiametral cells, 
however, increase in size at approximately the same rate as do 
the cells themselves. I am therefore disposed to think that the 
inseparation of the chlorophyll is the result of the failure of the 
isodiametral cells to stretch in the direction of the growth-axis ; 
and this supposition is strengthened when it is remembered 
that positive fragmentation t is more readily brought about in 
the lower part of the leaf, where the isodiametral cells are larger, 
than near the apex. Now, the occurrence of chlorophyll bodies 
in a group so high in the scale as Selaginellace@ is quite excep- 
tional; hence S. Martensii would seem to be the descendant of some 
* On a hasty view these bands may be taken for plasmolytic threads, which, 
of course, they are not, as can be seen on plasmolyzing the cell. 
t Possibly negative as well; but I have no notes upon this point. 
