. Practical text-book of plant physiology. Plant physiology. PERMEABILITY OF WOOD TO AIR 195 Now cut a few centimeters from each end and fasten the end of the branch originally uppermost to a glass tube 6 cm. in length by means of a section of pressure tubing (rubber). Now connect the glass tube with an air pump, or filter pump, and dip the lower end of the twig in a solution of ferric oxychloride. This may be made by adding 3 parts of water to 1 of the officinal preparation of liquid ferri oxychl- orati, which may be procured of pharmacists. Exhaust the air from the upper end of the branch. I
. Practical text-book of plant physiology. Plant physiology. PERMEABILITY OF WOOD TO AIR 195 Now cut a few centimeters from each end and fasten the end of the branch originally uppermost to a glass tube 6 cm. in length by means of a section of pressure tubing (rubber). Now connect the glass tube with an air pump, or filter pump, and dip the lower end of the twig in a solution of ferric oxychloride. This may be made by adding 3 parts of water to 1 of the officinal preparation of liquid ferri oxychl- orati, which may be procured of pharmacists. Exhaust the air from the upper end of the branch. If the fluid exuding from the branch, a quarter of an hour later, is colorless, cut away a few centi- meters from the lower end of the branch and immerse the newly cut surface in the liquid. Repeat at same interval until the brown fluid appears at the upper end of the branch. The length of the branch when this occurs gives the maximum extent of free air com- munication in the vessels. The liquor is colloidal and may not be forced through membranes. If the first test has been performed with a twig two years old, repeat with one of the same species five or six years old, and note the increased length of the free air communication. The results will be approximate. 269. Permeability of Wood to Air. Make some rods of wood from the outer portion of newly-felled trees of Abies, or Taxus, which are entirely free from dry rot, and insert the short arm of one end in a U-tube and seal tightly with wax. The long arm. Fig. 96. Demonstration of the length of air-passages in woody stems. a, filter pump attached to water tap. b, large glass tube in the lower end of which is fixed a branch of chestnut, standing in a dish containing coloring fluid, or injection material. After Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original
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