22 POROSITY OF WOOD. 
year, so that the plant may be treated as an annual. Its tubers may likewise be 
preserved in dry earth or sand all winter, like those of the dahlia, or in boxes or 
drawers. 
Datura (Bmgmansia) Arbor ea. — This plant has been kept all winter, in a pot, 
in a north shed, in a dormant state, and planted out in the open ground late in 
spring with success. 
From incidental observation, there is little doubt but Rhus semialata may be 
kept all winter in a pot in a north shed. 
Very probably there are many other plants, which have not yet been tried to be 
kept dormant during winter, but which will prove susceptible of that mode of 
management. 
THE CROCUS. 
There are curious phenomena exhibited in flowers, by the expansion and con- 
traction of their parts of fructification, yielding protection from wind and rain, and 
the dews of the night. The crocus is constantly influenced by atmospheric 
changes, and may also be acted upon in a similar manner by artificial means. The 
following results, among others, were submitted in the spring of 1831 : — 
The flowers having been gathered at night, when their corollas were perfectly 
closed, were placed at the distance of nearly a yard from two lighted candles, and 
in a temperature of 50° Fahr. In this situation and warmth they remained two 
hours, but their petals remained nearly closed. 
Other flowers were gathered at the same time, and being entirely excluded from 
light, were submitted to a warmth of 95°, the temperature being very gradually 
raised from 65°. Their continuance during two hours in this situation occasioned 
but very little change in them. 
Others were also gathered, and placed between two lighted candles at four inches 
from each, and in a temperature of 70° to 75°. These flowers, in rather less than 
an hour, were as fully expanded as in the mid-day sun. 
POROSITY OF WOOD. 
The porosity of wood is so remarkable that air may be transmitted in a profuse 
stream, by blowing with the mouth through a cylindric piece of dry oak, beech, elm, 
or birch, about two feet long. If a piece of wood or stone be put in water, and 
placed in the receiver of an air-pump, by withdrawing the external air, the air 
which has been scattered through the pores of these bodies will issue from every 
point of their surface, and rise in a torrent of bubbles. In like manner mercury is 
forced through a piece of dry wood, and made to fall in the form of a shower. 
