346 O. K Beecher — Origin and Significance of Spines. 



Lastly, the general spininess of climbing plants and bram- 

 bles is a well-known and conspicuous character. Kerner 38 says 

 that " most, if not all, plants which weave into the thicket of 

 other plants are equipped with barbed spines, prickles and 

 bristles." These spinifonn processes seem to fall naturally 

 into two classes. First, those produced by the suppression of 

 stipules, leaves, petioles, branches, etc., and second, those ap- 

 pearing as simple eruptions on the surface. 



71 72 73 



Figure 71. Leaf of Ratan, JDcemonorops hygrophilus. Reduced. (After Kerner.) 

 Figure 72. Leaf of Ratan, Desmoncus polyacanthus. Reduced. (After Kerner.) 

 Figure 73. Bramble, Rubus squarrosus. Reduced. (After Kerner.) 



The suppression of normal plant organs into special struc- 

 tures, as tendrils and claspers, is extremely common, and, as 

 already shown, this process if carried far enough without com- 

 plete suj^pression will favor the production of a spiniform 

 growth representing the axial elements of the organs. The 

 classes of organs thus affected are practically the same as those 

 in desert plants, though varying somewhat in manner and de- 

 gree. 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 necessary to give a long list of 

 examples among the climbers, illustrating the suppression of 

 organs into spines. Although apparently not of rare occur- 

 rence, 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 suj)pression of a number of the 



