52 



MORPHOLOGY OF STEMS. 



91 



by coiling in the opposite din-diem, as the Bean (Phaseolus), 

 the woody Aristolochia Sipho, the Morning Glory (Fig. 91) an<l 



other Convolvu- 



lace;e. The 1 )od- 

 dcr. a leafless par- 



^^^^ asitie plant of the 



latter family, not only pi ins Hipport by coiling 

 on the steins of other plants, but l>y attachment, 

 through the development of sucker-like discs, 

 along the whole contiguous surface. (Fig. 77.) 

 The various actions through which plants elimb, 

 and the attendant phenomena, are physiological, 

 and will be treated in the second part of this 

 Text Book. The most complete and satisfac- 

 tory discussion of the subject, of a readable sort, 

 is that of Darwin's volume, referred to in a 

 preceding note. 



101. Leaf-Climbers are those in which support is gained by the 

 action, not of the stem itself, but of the leaves it bears ; in most 

 by the coiling or clasping of petioles, as in Clematis, Maurandia, 

 Tnipa-ohini, and Solanum jasminoides (Fig. 235) ; in some by 

 the incurvation of leaf-blades or portions of them, as in Adlu- 

 mia : or by an extension of the midrib into a hook or short ten- 

 dril, as in Gloriosa ; or by the transformation of some of the 

 blades of a compound leaf into hooks or tendrils, as in C'oba-a 

 and the Pea. 



102. Tendril-Climbers (Fig. D2-95) are those in which the 

 prehension is by a tendril, a slender filiform body, either simple 

 or branched, specially adapted to the purpose, and capable of 

 coiling, either to secure a hold, or to draw the stein up to the 



coil or circle from the inside: Molil, Palm, Braun. and the l)e( 'andolles 

 adopt this, and the latter insist on it. Such authority should lie decisive, 

 it" ((HiiiiKiii usaue and popular sense \\ent along with it. But some of the 

 botanists following Linna-us adopted the reverse view ; and to the promt 

 writer, as to Bcntham and Hunker, Darwin, Kichler, and in part <!. Ileiislow. 

 it \\as so natural to view the coil from the outside that we without concert 

 adopted this position and mode of expression. A right-hand coil, or one 

 turning to the right, with us, is one the turns of which pass from the left to 

 right of a bystander who confronts the coil. It is in this sense that a com- 

 mon screw is called a, right-handed screw, and that the right bank of a river 

 is that to the right of the person who follows the course of the stream. So 

 natural is this, that even on a map or plate, which has face and back, and 

 therefore a right and left of its own, the figures occupying its right or left 

 portions are understood to be those which are toward the right or the left 

 hand of the observer who stands before it. 



Kl! '.!]'. I >pxtrornely twining stem of Morning Glory, Ipomoea purpuroa. 





