OF MOVEMENT IN PLANTS. 55 
conditions of nutrition,—we must recognize the probability of a gradual modification in 
uniformity, as also of a gradual cessation of motion, and the impossibility of the activity 
being prolonged or even shortened ; unless conditions of permanent contact and irritation 
are established, when maturity is accelerated. As will appear later, the motion resolves 
itself into an expression of the resultant of activity in two tissues, one of which is con- 
tinually growing, while the other is as continually becoming less active, and the cessation 
of motion must then be determined when the latter gains complete ascendancy over the 
former, and thus permanently destroys the equilibrium of growth. 
Internal to all the histological elements thus far discussed, lie the xylem portions of 
the vascular bundles. These, however, are widely separated. They are seven in number, 
the three largest traversing the lower region of the tendril arm. As elements of perma- 
nent structure, they must undoubtedly serve in a degree to supplement the mechanical 
value of the bast, but to this they are obviously very subordinate. Within the vascular 
zone is the somewhat large pith which, especially at the base of the tendril arm, early 
develops what De Bary ' designates as a “lysigenetic intercellular cavity,” to the extent 
that the organ becomes hollow for a considerable distance from its base. This also charac- 
terizes the petiole of both tendril and leaf, in each of which the same structural elements 
appear, and in much the same relative positions. 
Of the elements thus considered, we must regard the vibrogen, collenchyma and bast 
as of primary importance, and that they bear a definite relation to the circumnutation of 
the tendril, and to its behaviour under the influence of irritation, can hardly be doubted 
in the light of the facts to be presented in the following pages. 
GROWTH IN LENGTH.—In vigorous vines, the largest tendril arm often exceeds 30 cm. 
in length. The extreme lengths of the tendril arm, during the entire period of circum- 
nutation, may generally be taken as ranging from 8 em.to 35 cm. As this great elonga- 
tion must occur within the very limited period of two days, it Indicates a most rapid 
organizing process, as the following determinations will show. Moreover, it must be 
borne in mind that the cessation of growth in length and of circumnutation is simul- 
taneous. The following determinations have been obtained. An arm just uncoiled from 
the bud measured 12 cm. in length. One day later it had increased to 14.8 cm., and on 
the following day to 18.3 cm., thus giving a total increase in length of 6.3 cm., or one- 
half the original. August 8th, five tendril arms, but a short time in action, were measured 
and marked. The Monday following (10th) all except one were found to have coiled 
about themselves or other objects. The coils were drawn out and measured with the 
following results :— 







1 2 3. 4 5 
August Sth...... . 12.0 | 12.4 d7 7 NUTO 4 bem: 
| | 
| | 
GB, Hier cane | 24.5 | 19.0*| 25.0*! 20.5*| 33.0 * 
| | — 
GAIN ce cise ates eas | 12.5 |. 6.6 ok | 10.1 1529 
| | 

* Indicates those which could not be fully straightened. 

* Comparative Anatomy of Phenogams and Ferns, Eng. Ed. 200. 
