, and on
two nights afterwards they were again exposed to the same temperature, but
this time during 1 h. 30 m. On neither occasion was a single leaf, whether
pinned open or free, injured; and this surprised us much, considering its
native tropical African home. Two plants were next exposed (March 16th) for
30 m. to a clear sky, the temperature of the surrounding grass being now
lower, viz., between -3o and -4o C., and all four pinned-open leaves were
killed and blackened. These two plants bore 22 other and free leaves
(excluding some very young bud-like ones) and only two of these were killed
and three somewhat injured; that is, 23 per cent. were either killed or
injured, whereas all four pinned-open leaves were utterly killed.
On another night two pots with several plants were exposed for between 35
m. and 40 m. to a clear sky, and perhaps to a rather lower temperature, for
a thermometer on a dial, 3 feet high, close by stood at -3.3o to -3.8o C.
In one pot three leaves were pinned open, and all were badly injured; of
the 44 free leaves, 26 were injured, that is, 59 per cent.
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