228 e General Notes. [March, 
ambiguum, The genus Aplopappus is greatly extended, including 
the old genera Prionopsis, Eriocarpum, Pyrrocoma, Homopappus, 
Sideranthus, Isopappus, Stenotus, Ericameria and Macronema. 
The five species of Aphanostephus and the seventeen species of 
Townsendia are briefly characterized, and a systematic synopsis 
is given in each case. In discussing the genus Erigeron the 
author says: “It can be limited only by taking into account a 
combination of characters, and insisting here upon one, and there 
upon another.” _ Aster graminifolius, of Gray’s Manual, is hereafter 
to be known as Evigeron hyssopifolius. Erigeron vernum is likewise 
changed to E. nudicaulis. The genus Aster is accepted in the 
wide extent assigned it by Bentham and Hooker in the Genera 
Plantarum. The revision of this genus is not yet completed, but 
enough has been done to indicate that there will be but little 
change made in it as we have known it in Dr. Gray’s works here- 
tofore. The remainder of the order is still to be revised. 
THE SENSITIVENESS OF THE Root-TIP OF THE SEEDLING.—We 
believe that there is no structure in plants more wonderful, as far 
as its functions are concerned, than the tip of the radicle. If the 
tip be lightly pressed or burnt or cut, it transmits an influence to 
the upper adjoining part, causing it to bend away from the affected 
side; and what is still more surprising, the tip can distinguish 
between a slightly harder and a softer object by which it is simul- 
taneously pressed on opposite sides. If, however, the radicle is 
pressed by a similar object a little above the tip, the pressed part 
does not transmit any influence to the more distant parts, but 
_bends abruptly towards the object. If the tip perceives the air to 
be moister on one side than the other, it likewise transmits an 
influence to the upper adjoining part, which bends toward the 
source of moisture. When the tip is excited by light, the adjoin- 
ing part bends from the light; but when excited by gravitation, 
the same part bends towards the center of gravity Darwin's 
“ The Power of Movement in Plants.” 
INFLUENCE OF LIGHT ON THE RESPIRATION OF SEEDS.—Planchon 
read a paper before the Paris Academy of Sciences, at its meeting 
on Nov. 22d, detailing experiments upon this subject. The 
experiments were made on the castor-oil plant and the bean 
(Phaseolus). As in previous experiments, a good deal more oxy- 
gen was observed in light than in darkness. The castor-oil seeds 
exhale slightly more CO, in darkness than in light, but the opp 
site was the case with the seed of the bean, In darkness the 
ratio of CO, to O was for the bean at least one-third superior to 
that for the castor-oil plant, but prolongation of the experiment 
tends to bring the relation equal to unity, whatever the original 
value. For a given quantity of oxygen absorbed, the seed placed 
in darkness exhales more CO, than that kept in light. While im 
light there is always less CO, exhaled than oxygen absorbed, the 
