278 



EVOLUTION OF PLANTS 



ing plants are very numerous, and the tall trees are 

 loaded down with giant creepers which are striving to 

 reach the light overhead. The means by which this is 

 accomplished are various. Some plants climb by twin- 

 ing their slender stems about the support (Fig. 60, A), 

 like the morning-glory or hop ; others develop special 



climbing organs, ten- 

 drils (B, C), which 

 are either modified 

 branches or parts of 

 leaves. The climb- 

 ing rattan palms, and 

 some other tropical 

 lianas, simply recline 

 over the branches of 

 trees, holding on by 

 stout hooked prickles. 

 A smaller number of 

 FIG. 60 (Climbing plants). -A, twining creepers, like the ivy 



stems of Mandevillea suaveolens ; I, leaf- g,nd various trODlCal 

 scar; B, leaf of sweet-pea with the ter- 

 minal divisions transformed into tendrils, aroids, C 1 1 HI b by 

 ten; C, twining leaf-stalk of Solarium ,. , 



jasminoides. means oi short root 



tendrils. 



PARASITES AND SAPROPHYTES 



Not to be confounded with the epiphytic plants are 

 the true parasites, such as the mistletoe and dodder. 

 Some, like the mistletoe and its numerous tropical re- 

 lations, species of Loranthus, are only partially para- 

 sitic, being provided with more or less chlorophyll, so 

 that they are capable of carbon assimilation. In the 



