In the other pot
3 leaves were pinned open and all were killed; four other leaves were
prevented from sleeping by narrow strips of stiff paper gummed across them,
and all were killed; of 24 free leaves, 10 were killed, 2 much injured, and
12 unhurt; that is, 50 per cent. of the free leaves were either killed or
much injured. Taking the two pots together, we may say that rather more
than half of the free leaves, which were asleep, were either killed or
injured, whilst all the ten horizontally extended leaves, which had been
prevented from going to sleep, were either killed or much injured.
Cassia floribunda.--A bush was exposed at night for 40 m. to a clear sky,
the temperature on the surrounding grass being -2o C., and not a leaf was
injured.* It was again exposed on
* Cassia laevigata was exposed to a clear sky for 35 m., and C. calliantha
(a Guiana species) for 60 m., the temperature on the surrounding grass
being -2o C., and neither was in the least injured. But when C. laevigata
was exposed for 1 h., the temp. on the surrounding grass being between -3o
and -4o C.
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