ORIGIN AND SIGNIFICANCE OF SPINES 89 



The classes of organs thus affected are practically the same 

 as those in desert plants, though varying somewhat in man- 

 ner and degree. The consolidated type of plant body is 

 naturally absent, for in this respect the diffuseness of 

 climbing plants is quite antithetical. It does not seem nec- 

 essary to give a long list of examples among the climbers, 

 illustrating the suppression of organs into spines. Although 



71 72 73 



FIGURE 71. Leaf of Ratan (Dcemonorops hygrophilus). Reduced. (After 

 Kerner.) 



FIGURE 72. Leaf of Ratan (Desmoncus polyacanthus). Reduced. (After 

 Kerner.) 



FIGURE 73. Bramble (Rubus squarrosus). Reduced. (After Kerner.) 



apparently not of rare occurrence, spines produced in this 

 way are not as common as among desert plants. Two figures 

 of the pinnate leaves of Ratan are introduced here to show 

 the suppression of a number of the terminal leaflets into 

 spines (figures 71, 72). In Machcerium the stipules are 

 converted into thorns. 62 A tropical Bignonia (B. argyro- 

 violacea) has normal full-sized simple leaves, and suppressed 

 leaves bearing two opposite leaflets on one stalk, and ending 



