(-3.3o to -3.8o C.), but when looked at after 1 h.
had fallen to 22o F. (-5.5o C.); so that the pot was perhaps exposed to
rather a lower temperature than on the two first occasions. Eight leaves
had been pinned out, some close to the cork and some above it, and on the
following morning five of them (i.e. 63 per cent.) were found killed. By
counting a portion of the leaves we estimated that about 250 had been
allowed to go to sleep, and of these about 20 were killed (i.e. only 8 per
cent.), and about 30 injured.
Considering these cases, there can be no doubt that the leaves of this
Oxalis, when allowed to assume their normal vertically dependent position
at night, suffer much less from frost than those (23 in number) which had
their upper surfaces exposed to the zenith.
Oxalis carnosa.--A plant of this Chilian species was exposed for 30 m. to a
clear sky, the thermometer on the grass standing at -2o C., with some of
its leaves pinned open, and not one leaf on the whole bushy plant was in
the least injured. On the 16th of March another plant was similarly exposed
for 30 m.
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