CHAP. II. TENDRILS. 71 



Sometimes the tendril is simple or undivided, Modifica- 

 as in that of Lathyrus Aphaca or Yellow Vetchling, 

 and sometimes it is branched or compound, as in 

 that of the genus Vicia (PL III. Fig. 8), thus 

 multiplying its chances of meeting with support. 

 If it issues from the stem or branch it is generally 

 at the axil of the leaves ; if from the petiole, at the 

 extremity ; and if from the leaf itself, at the apex, 

 as in Gloriosa superba and Flagdlaria indica, but 

 in the Vine it issues from a point opposite to the 

 insertion of the leaf. It is sometimes of use to 

 the botanist in the discrimination of species, of 

 which it enters even into the essential character, as 

 in the genus Lathyrus. 



In its origin it is generally straight and in some Origin, 

 cases still continues so, but in plants in which it is 

 finally spiral it soon begins to assume the spiral 

 form, extending itself to the nearest object of sup- 

 port, and twisting itself firmly around it, so as to 

 prop up the plant till it can send out new tendrils 

 to lay hold of objects still higher. 



In some plants the tendril, after completing a cer- Anoma- 

 tain number of circumvolutions in one direction, ies * 

 twists itself spontaneously about and performs its 

 future circumvolutions in a contrary direction. 

 This is a phenomenon not easily accounted for. 

 In the Virginian Creeper, Hedera quinquefolia> or, as 

 Dr. Smith thinks it ought to be called, Vitis quinque- 

 folia,* the tendril which issues from the axil of the 

 * Smith's Introduction, p. 225. 



