706 CLIMBING PLANTS. 



of a rocky wall, develop climbing roots close below the growing shoot-apex. These 

 roots speedily reach the wall and fasten the portion of the stem from which they 

 arise to it. This continues slowly, the shoot-apex continually creeping higher up 

 over the substratum. This is the simplest way in which climbing stems become 

 attached. The process by which those of the often -cited Tecoma radicans are 

 affixed is much more complex. These stems shun the light in a marked degree. 

 If TecoTna radicans is planted in front of a wall covered with trellis -work, the 

 actively growing shoots turn away from the light, slip behind the trellis-work, and 

 adhere closely to the wall by those portions of the stem at which climbing roots 

 appear. So soon as they come in contact with the hard substratum the small 

 pale rootlets grow out from the cushions as a fringe of threads which cling very 

 firmly to the wall. The growing shoot never leaves the wall, but keeps close to 

 it, always seeking the darkest places under projecting tiles, ledges, and cornices, 

 attaching itself at intervals by fresh clamp-roots. 



The most remarkable method by which shoots destined for climbing reach a 

 wall which will afford them a support is observed in several tropical Bignoniaceas 

 related to Bignoiiia unguis, one of which, Bignonia argyro-violacea, growing by 

 the Rio Negro in Brazil, is represented in fig. 170. This plant bears two kinds 

 of leaves : simple leaves, tlie blades of which attain to a considerable size, and 

 others which, like the leaves of the vetch (Lathyrus), bear two opposite leaflets 

 on one stalk and end in a structure which divides into three limbs with pointed 

 hooked claws, and which is not unlike the foot of a bird of prey. 



The development of this clawed, grasping organ always precedes that of the 

 leaflets, so that in the youngest stages the green leaflets only appear as minute 

 scales. Leaves ending in claws are only found on stems which, so to speak, have 

 to seek a firm, safe support for the flowering and fruit - bearing shoots to be 

 developed later on. These stems, however, are thin, much elongated, and are always 

 pushing out new internodes. They hang down as long threads from the tree, whose 

 bark is already quite covered, and which offers no space for a new settlement, and 

 are easily set in motion by the action of the wind. At the end of each thread can 

 be seen two young leaves placed opposite one another, on each of which only the 

 three hooked limbs are at first developed, appearing to be extended for prehensile 

 purposes, just as in a bird of prey. If the shoot oscillating in the air fails to 

 encounter an object which it can seize with its claws, the latter fold back, and the 

 leaflets are developed. Before the following day the filamentous stem has produced 

 a new portion similarly equipped. These fresh claws are again extended, and the 

 supple stem again sways in the wind, in the hope of being able to catch hold of 

 a firm object. The same thing is repeated day after day until some suitable 

 anchorage comes within reach of the elongating shoot. Now is the time for the 

 development of the clamp-roots, which have to fix the stem to the substratum 

 still more firmly than the claws could do. The climbing roots are really already 

 present at each node of the filamentous stem as small protuberances, but they 

 remain quite short until such time as the swaying shoot effects its attachment. Then 



