Some leaves showed that
they had been slightly injured by not expanding during the whole of the
next day, though they afterwards recovered. As all the leaves which were
pinned open were killed, and only about a third or fourth of the others
were either killed or injured, we had some little evidence that those which
were prevented from assuming their vertically dependent position suffered
most.
The following night (17th) was clear and almost equally cold (-3o to -4o C.
on the grass), and the pot was again exposed, but this time for only 30 m.
Eight leaves had been pinned out,
[page 288]
and in the morning two of them were dead, whilst not a single other leaf on
the many plants was even injured.
On the 23rd the pot was exposed for 1 h. 30 m., the temperature on the
grass being only -2o C., and not one leaf was injured: the pinned open
leaves, however, all stood from ? to 3/4 of an inch above the cork.
On the 24th the pot was again placed on the ground and exposed to a clear
sky for between 35 m. and 40 m. By a mistake the thermometer was left on an
adjoining sun-dial 3 feet high, instead of being placed on the grass; it
recorded 25o to 26o F.
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