PHYSIOLOGY 



261 



The direction of the revolving movements, and accordingly also of 

 the windings, of most stem-climbers is constant. The twining stems 

 are for the most part sinistrorse (Convolvulus, Phaseolus, Pharbitis, 

 etc.). Seen from above, the windings run from the north towards the 

 west ; that is just the reverse of the movement of the hands of a watch. 

 Viewed from the side, the windings ascend the support from the left 

 below to the right above (Fig. 205). Dextrorse stem-climbers with 



I 



51 



Fig. 205. — A sinistrorse stem-climber, 

 Pharbitis Mspida. The upper 

 leaves remain small for a long 

 time. 



Fig. 206. — A dextrorse stem-climber, 

 MyrsiphyUum asparagoides. The 

 short lateral shoots have de- 

 veloped phyllocladia. 



windings from east to west occur less frequently (Hop, Honeysuckle, 

 Polygonum Convolvulus, etc.). In the example chosen for illustration 

 (MyrsiphyUum asparagoides, Fig. 206) the undeveloped condition of the 

 lateral members in comparison with the elongated internodes of the 

 stem is very apparent. A very few plants, such as Blumenbachia 

 lateritia, Hibbertia dentata, and Scyphantus, seem able to climb equally well 

 either to the right or to the left. A similar irregularity is shown in 

 Solanwn Dulcamara, which, however, rarely winds, and then only under 

 special circumstances. 



