232 General Notes. [April, 
above ground any great amount of moisture, if they do any at all, but 
the slight transpiration which had been going on from stems and young 
shoots is now checked. The small amount of moisture which thè roots 
can take from the parched soil is not without speedy effect upon the 
branches and buds to which it is carried. The buds soon open. Butin 
the spring of 1875, when there was not a cloud to be seen in May, and 
the west wind at evening brought little relief from the scorching drought 
of the day, and the baked crust of the soil everywhere showed no trace 
of moisture, the trees put forth their leaves as usual! Now the first case 
is easily explained; how about this one, which seems so different ? 
At the outset, Professor Ernst admits that the individual nature of the 
plant, the age, the condition as regards health, etc., must be carefully 
investigated. This he has not yet done. He goes on, however, to say 
that it is generally understood that the only external excitant to growth 
is the warmth of the air. Since in the dry season there is, as he states, a 
difference between the temperature in the sunlight and at night of about 
twenty-seven degrees Fahr., this must cause very great changes in the 
volume of the gases held in the spongy tissues of the tropical trees. The 
pressure is very variable, and he assumes that the fluctuations must cause 
motions of nutrient liquid. He further assumes that when these juices 
are brought to the terminal cells of a bud, growth must result, and the 
leaves must unfold.’ It must be confessed that Professor Ernst has 
made a fair use of Krutzsch’s observations in regard to the temperature 
of stems and twigs as affected by the surrounding temperature, and he 
appears to have skillfully applied the mechanical theory to this case, but 
he has not as yet done much to solve the riddle of periodicity of vege- 
table rest. 
ECCENTRICITY oF THE Pirra or Raus TOXICODENDRON. — My at- 
tention was drawn to this subject by the January NaruraLIst. As is well 
known, this handsome but much-dreaded climber, so common in all our 
woodlands, has the habit of adhering tightly to the trees which it ascends 
by a multitude of aerial rootlets, which often cover its stem and give it 
the appearance of being embedded in a cushion of moss. 
The results of my investigations on the stems of this plant are some- 
what curious. The fact itself that the pith, wherever the vine is found 
adhering closely to living trees, lies very near the outer side, leaving 4 
largely disproportionate amount of the woody tissue on the side next the 
tree, is, so far as I have observed, universal. The following observations 
will give an idea of this disproportion : — 
In a vine 5} lines in diameter the distance from the centre of the pith 
to the inner margin was 43", and to the outer only 3. This propor- 
tion held uniformly for various heights from the ground. The measure- 
ments included the bark, which, as well as the annual rings, partook of 
the general tendency, and was much thinner on the outer side. 
A larger vine, upwards of an inch in diameter at the base, had climbed 
4 
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EA E y ORNES aa ATES 
