182 



BOTANY 



PART I 



These are the CLIMBING PLANTS or LIANES and the EPIPHYTES. They 

 are specially characteristic of the tropics, though also represented in our 

 native flora. 



1. Lianes OP Climbing 1 Plants ( s9 ). These are able without great 

 expenditure of material in the construction of columnar stems to raise 

 their foliage above the shade of the forest and obtain stronger light. 

 Their slender stems climb by the help of the shoots, trunks, and 

 branches of other plants. It is the rope-like stems of lianes that 

 render many parts of the tropical jungle 

 almost impenetrable. 



Climbing is effected in a number of 

 different ways. Some plants SCRAMBLE by 

 means of hooked lateral shoots, by hairs and 

 prickles, by a combination of these or by 

 means of thorns (e.g. Galium aparine, Roses, 

 Solanum dulcamara) ; others climb by means 

 of roots (ROOT-CLIMBERS, e.g. Ivy, many 

 Araceae), or by twining stems (TWINING 

 PLANTS, e.g. Hop, Scarlet Runner Bean) ; in 

 others tendrils are developed as special organs 

 of attachment (TENDRIL CLIMBERS). Tendrils 

 are slender, cylindrical, branched or unbranched 

 organs ; they are irritable to contact (cf. p. 

 353), and thus able to encircle supports to 

 which they attach the plant. They may be 

 METAMORPHOSED SHOOTS (stem-tendrils) as in 

 the Vine, the Wild Vine (Fig. 210), and the 

 Passion-flower. In other cases they are 

 TRANSFORMED LEAVES as in the Gourd, the 

 Cucumber, and Lathyrus aphaca (Fig. 209) ; 

 in the last example the functions of the leaf- 

 R, R, stem -tendrils, blade, which has become the tendril, have 

 (I nat. size. After NOLL.) b een assumed by the expanded stipules. In 

 the Pea (Fig. 208) and many other cases the 

 uppermost leaflets of the pinnate leaf form a branched tendril. 



In some forms of the Wild Vine (Parthenocissus quinquefolia) and in 

 other species of this genus such as P. tricuspidata (Fig. 210) the branched 

 tendrils bear attaching discs at their tips and can thus fasten the plant 

 to flat surfaces. 



5 The great width of the vessels and sieve-tubes is characteristic of almost all 

 lianes. In tropical climbers anomalous secondary growth is frequently met with, 

 resulting in a subdivided woody mass that renders the long rope-like stems capable 

 of withstanding bending and twisting. A very peculiar structure is exhibited by 

 many lianes of the Bignoniaceae, the wood of which is cleft by radially-projecting 

 masses of bast (Fig. 212). The primary stem of the Bignoniaceae shows the 

 ordinary circular arrangement of the vascular bundles. Wood and bast are at first 



no. 2io.-pa^en OC 



