248 Canadian Record of Science. 



bast from the other tissues for a distance of one or more 

 centimetres. Under such conditions of strain, it is also to 

 be note that the tissues along the lower side of the ten- 

 dril, or the concave side of the spring, do not elongate, but 

 the softer tissues on the opposite side sutler a strong com- 

 jaression and form a spiral around the straightened and 

 resisting bast as a central axis. The compression of parts 

 is to be observed in the strong, transverse corrugations in 

 the surface, as also in the formation of minute drops of 

 moisture which exude from the surface over the entire area 

 of compression, but more particularly alo g the lines of 

 vibrogen, where also the corrugations are the most strongly 

 defined. 



According to the weight or strain imposed, the spirals 

 will be open or closed. This is conspicuously true where 

 vines hang by their tendrils, or where any resistance is 

 offered to attachment. But it must be kept in mind, as 

 our previous considerations show, that the vine cannot be 

 drawn to a support — it must first approach a support in the 

 natural course of growth, and then become secured to it. 

 In harmony with this, it is found that when the strain is 

 slight, or when the vine in growing advances toward the 

 support, the coils become correspondingly closer. 



Eigid support is not essential, nor need the object be 

 large. The requirements are met if it be sufficiently irrita- 

 ting, and possess a very moderate degree of stability. 

 Small pebbles, bits of grass and similar objects lying upon 

 the ground, and even small particles of dirt, hardened by 

 rain, have been found sufficient to meet all requirements 

 and cause the formation of double spirals in a normal 

 manner. 



Wilted tendrils may be drawn out without any appre- 

 ciable resistance, while those which have coiled without the 

 influence of a supporting object, and which rarely if ever 

 coil regularly, may be drawn out with a force which rarely 

 exceeds 40 gr. It thus appears that the strain required to 

 draw out the coils of a tendril which is comparatively fresh, 

 is an expression of the force — or, in other words, the ten- 

 sion — developed in all the softer tissues, and required to 



