386 Ewart — The Action of Cold and of 
In Chara foetida about 10 minutes’ exposure to cooled and 
concentrated light (8 to 10 S) is sufficient to completely 
bleach a naked and non-encrusted end-cell. The chloro- 
plastids on the under surface bleach first, those on the upper 
at the same time or immediately afterwards, and those at the 
sides a minute or two later. If the exposure and bleaching 
are localized, the cell may remain living, and the majority of 
the bleached chloroplastids retain their original position, so 
that, although a few come free and are carried away by the 
rotating plasma, no naked areas are formed, as was the case 
in Pringsheim’s experiments 1 . The rotating plasma experi- 
ences a certain check at the exposed area, and finally the 
current may cross the cell at this point and return up the 
other side, the endoplasm being thus divided into two distinct 
rotating masses. Such cells always die when returned to 
normal conditions. By suddenly exposing preparations of 
end-cells of Chara to light, it is easy to show that the bleached 
portions have no power of evolving oxygen by C (^-assimi- 
lation ; and when such end-cells are kept in 2 °/ o glycerine, 
starch-grains are formed in the green chloroplastids, but not 
in the colourless ones, which have therefore not only lost 
the power of C 0 2 -assimilation, but also of starch formation. 
Similar results were obtained with leaf-cells of Elodea, 
and although it has not been found possible to entirely bleach 
all the chloroplastids of a cell without killing the latter, still 
living cells may be obtained in which a portion of the chloro- 
plastids are entirely bleached, and the rest are pale yellow 
to yellowish green. The latter may become normally green 
again, and are able to form starch, whereas however long the 
leaves may be kept in a f / o sugar-solution, no starch-grains 
appear in the bleached chloroplastids. Living end-cells of 
Chara have been observed in which the bleached chloro- 
plastids were retained for an entire year without undergoing 
any further change 2 , and hence apparently light not only kills 
and bleaches the chloroplastids, but also converts its proteid 
1 Pringsheim, Pringsh. Jahrb., Bd. xii, 1882, pp. 326-344. 
2 Journ. Linn. Soc., 1897, Vol. xxxi, p. 573. 
