OBSERVATIONS UPON THE PHENOMENA OF PLANT-LIFE. 307 



bars and glass above it, sometimes to tbe height of two feet, and as it increased 

 in length, was pushed along against them. The extent and velocity of the 

 terminal motion were doubtless greatest in August, when growth was most 

 rapid. The record, however, was made in November. The time occupied in 

 each revolution Avas variable, and the long diameter of the ellipse described, 

 ■which was horizontal, measured about two inches. 



'J 



THE TENDKILS 



of the squash-vine were produced at the nodes, and the main stalk was hollow, 

 and divided into several branches at a point three or four inches distant from 

 the vine. These branches spread out in various directions, and attained a 

 length of six or eight inches. Each branch gradually straightened out from 

 the coil in which it first appeared, and increased in length. When about two- 

 thirds developed it began to revolve so that its hooked tip described an ellipse 

 several inches in diameter. Its revolution was made by a series of bendings, 

 in such a way as not to twist itself. The tendrils moved in the same direction 

 with the tip of the vine, but somewhat irregularly both as to time and to the 

 figure described. During the day ihe ellipse was broad, and at night long and 

 narrow. Usually the motion was scarcely perceptible to the eye, but some- 

 times it moved two inches in five minutes. The average time of revolution 

 in November was about three hours. If touched by the finger on the sensitive 

 or inner side, the tendril bent towards the place where the finger was, and, not 

 finding it, straightened itself again. If, however, it came in contact with any 

 object to which it could cling, it bent at the point of contact, and the concave 

 curvature extended along the inside of the branch until the extremity was 

 wound closely around the support. Other branches would, also, fasten to the 

 same object, if possible. The tendril, thus attached, increased in size and firm- 

 ness, and soon coiled upon itself in a double reversed spiral, so as to exert a 

 strain on the support. All the branches having done this, they pull together 

 and must fail together, if at all. 



Another most obvious benefit derived from this double spiral is the elasticity 

 of the fastening, which greatly diminishes the danger of rupture by violence. 

 If the tendrils of the squash failed in finding a support, the branches then 

 coiled upon themselves, and the main stalk often turned back along the vine. 



THE HABITS 



of climbing plants have been studied by Mr. Charles Darwin and others ; but 

 this field for research is by no means exhausted. 



The tendrils of the grape-vine are not very sensitive, but fasten themselves 

 very firmly to a suitable support. The tendrils of the Cohcea scandens are long, 

 branching, and tipped with woody claws. They are extensions of the petiole 

 of a compound leaf, revolve actively, and attach themselves in a most marvel- 

 lous manner. AVhen a revolving branch has found a support, it contracts so 

 as to bring its extremities in contact with it. The other branches seek the 

 same object, and as they are sensitive on all sides, they fail in many cases to 

 secure a firm attachment with their claws. They therefore detach themselves 

 from their support, one at a time in succession, twist so as to bring their claws 

 into the proper direction, and then again make fast. 



It is well known that most plants grow toward the strongest light; but 

 climbing plants are sometimes exceptions. English ivy turns its young shoots 

 away from the light in order that they may come in contact with dark objects, 

 — such as rocks and trunks of trees, — to which they then attach themselves by 

 short roots. The tendrils of the Virginia creeper, or woodbine, are among the 



