40 GROWTH AND WORK OF PLANTS 



stems of an individual plant may extend in various directions. 

 The general position, however, of the plant is erect. Where a 

 number of individuals start very close together, in age the outer 

 ones may lean more or less under the influence of light and the need 

 for room. This is true with many shrubs which branch near the 

 ground or send up many stems from the underground portion. 

 Erect stems are self-supporting, the woody and supporting tissues 

 being sufficiently developed to give great strength and rigidity, 

 while the proportion in size and height is in harmony with the 

 supporting tissues. 



67. Climbing stems. Climbing stems are not self-supporting; 

 they climb upon or around other objects. The pumpkin, the 

 morning glory, the grape, Japanese and English ivy, climbing 

 bitter sweet, climbing poison ivy, the rattan, etc., are examples. 

 The rattan grows in India, often attaining several hundred feet in 

 length. The more slender species are used for wickerwork, etc. 

 Climbing stems secure themselves to the object of support in 

 various ways. Root climbers develop numerous aerial roots from 

 the stem which take hold in the crevices of the coarse bark of trees, 

 as in the climbing poison ivy, or they can lay hold of smoother 

 surfaces of trees or walls, as the English ivy. Tendril climbers 

 take hold of the object of support by long 

 slender outgrowths. In many cases these 

 tendrils are modified leaves or portions of 

 leaves. In the pea the terminal portion of 

 the leaf and leaflets (the midribs) forms 

 the tendrils which coil around the object of 

 ^support. In the squash and some other 

 cucurbits it appears that the tendrils are 

 the main veins of reduced leaves. In the 

 clematis, or virgin's bower, the petiole of the 

 leaf acts as the tendril and coils around 

 -fasts. the object. The dwarf tropaeolum climbs 



in a similar way. In the Japanese (or Boston) ivy the ends of the 

 branched tendril are broadened into thin, flat, disk-like objects, 

 which are applied closely to the smooth surface of the wall and 



u j- 



Japanese ivy with disk-like 



hold-f 



