216 



HUTCHINSON'S POPULAR BOTANY 



Aerial stems present a far greater variety of forms than those which 

 grow beneath the soil. In some cases the trunk is simple and unbranched, 

 as in the Palms, when it is called a caudex ; in others to wit, the stems of 

 most woody trees and shrubs the branches are numerous. A stem that 

 is weak and not woody, and which perishes annually down to the root, is 

 herbaceous. Then there are root-shaped stems and knotted stems ; ascending 



stems and trailing stems; 

 twining stems and climb- 

 ing stems ; and all these 

 may and do assume 

 a bewildering diversity 

 of forms cylindrical, 

 triangular, quadrangu- 

 lar, ribbed, compressed, 

 etc. How singular, for 

 example, is the mode of 

 growth of those glorious 

 tropical climbers, the 

 Bauhinias ! Here (fig. 

 275) is a drawing of 

 part of the stem of a 

 Demeraran species, 

 which the natives call 

 " bush-rope " and the 

 sailors " land-turtles' 

 ladders," and which 

 offers as neat an exam- 

 ple of Nature's wood- 

 carving as one could 

 wish to see. It is prob- 

 able that the undulating 

 central part of such 

 stems protects the sap- 

 conducting tissues of the 

 plants against strain. 

 The edges of the stem 

 are almost straight, and 

 form a sort of frame- 

 work to the sinuous middle part ; so that, as Kerner says, " in the case 

 of a longitudinal tension the frame only is affected at first," and " the 

 tissues in the centre can still uninterruptedly conduct the sap to and from 

 the branches which arise from its broad surface " (Natural History of Plants). 

 " Often three or four of these bush-ropes," says Dr. Hartwig, " join tree to 

 tree, and branch to branch ; others descending from on high take root as 



Photo by] IE. Step. 



FIG. 270. SNAKE'S HEAD (Fritillaria meleagris). 



A native Lily that grows in moist meadows. Its dull purple flowers are 



chequered with light and dark tints. The photo, which is two-thirds of the 



natural size, includes the rare white variety. EUROPE, W. ASIA. 



