48 D. P. PenhaUow — Tendril Movements in 



squash, a knowledge of the conditions favorable and adverse to 

 growth was sought. To accomplish this satisfactorily, observa- 

 tions were made through day and night for one week, at least 

 once each hour, generally at much more frequent intervals, and 

 every observation recorded was accompanied by record of local* 

 temperature, humidity, cloud, condition of the plant, etc., etc. 



The method of recording the tendril movements was as fol- 

 lows : — 



A board made two feet square, was provided with two pointed 

 legs by means of which — thrusting them into the ground — it 

 could be securely fixed in a vertical position. Upon the board 

 there were fastened several sheets of heavy white paper, so ar- 

 ranged that each could be removed in turn, without disturbing 

 the position of the board, (fig. 1). The recording board thus 

 prepared was then firmly fixed in a position at right angles to 

 the horizontal tendril. To prevent any accidental movement 

 of the latter from its proper position, a stake was driven by the 

 side of the vine at the node from which the tendril arose, and 

 the plant was then secured firmly to it. With the tip of the 

 tendril only one-fourth of an inch from the surface of the paper, 

 it was an easy matter to mark the position at any time with a 

 pencil. The position was noted whenever, from the rate of 

 movement and distance traveled, it was thought a change of 

 direction was about to occur. In this way the observations 

 were made at varying intervals, sometimes of one hour, some- 

 times of only one-half a minute, and many, originally taken,, 

 were finally eliminated from the results whenever they fell in 

 the same straight line. The time was always carefully noted, 

 as also all conditions of atmosphere and of the plant which 

 might have a possible bearing upon the movement. 



Tendrils. 



The tendrils of the squash are modified leaves, f and are 

 placed alternately opposite, an arrangement well adapted to 

 bring the plant between secure but elastic supports on either 

 side. They are composed of four or five long and slender fila- 

 ments — wholly devoid of external appendages by means of 

 which they can become attached to objects — borne upon a 

 stout stalk or petiole of from 6 to 10 cm in length. The arms 

 are of very unequal length. In vigorous vines the longest arm, 

 which is the first to develop, often exceeds 30 cm in length. 

 The extreme lengths of vigorously moving tendrils may gener- 



* The temperatures were taken from a thermometer hung by the side of the 

 plant, two feet above the ground. 



f The exact morphological nature of the tendril in Cucurbitacece is still a matter 

 of some donbt. It is variously regarded as a modified leaf, stipule or branch. 

 Evidence favorable to each of these views may be adduced. 



