EPIPHYTES 121 



that the main leaf-axis and its branches may all alike 

 take part in attaching the plant to a support. There is 

 no doubt that a similar general sensitiveness preceded, 

 in evolution, that localized and specialized sensitiveness 

 which, in other climbers, is confined to the tendrils. 

 This sensitiveness, which accompanies partial etiolation in 

 weak light, and which makes the evolution of the tendril 

 possible, is probably due to the fact that etiolated stems 

 and shoots, through their rapid growth, have soft tissues 

 with no strong woody elements during their sensitive 

 period. Sensitive movements can only be associated with 

 organs whose tissues consist of thin-walled cells, turgid 

 with water. 



There are not many native climbers in temperate 

 climates. In tropical rain-forests, tree-growth is so 

 luxuriant that the forest- floor is always plunged in partial 

 gloom. Climbers with great twisted woody stems sprawl 

 over the undergrowth, and loop themselves from tree to 

 tree, climbing towards the light they need so much. The 

 only woody climbers (lianes) we possess are the clematis , 

 honeysuckle, and ivy. 



Epiphytes. These are plants which pass their lives 

 perched upon the elevated parts of other plants, chiefly 

 the branches of trees. They are anchored to their sup- 

 ports in various ways, usually by clasping roots. As a 

 result of their position, they have a precarious water- 

 supply, and invariably show xerophytic characters. The 

 most common epiphytes are found among the lower plants, 

 lichens, liverworts, mosses, and ferns. The most abun- 

 dant epiphyte everywhere is the lichen, which shows 

 wonderful adaptations to extreme conditions. Generally, 

 however, epiphytes are only found in moist shady places, 

 and this is especially true of the flowering epiphyte, 

 which is rare in the temperate regions of the world. In 

 the Tropics, on the other hand, they form a feature of the 

 vegetation of the dripping forests, the home of the 

 epiphytic orchids and bromeliads. In this country we 

 have no true flowering epiphyte. Accidentally, however, 

 many plants are epiphytic. In humid mountain glens 

 we may often see plants growing on other plants ashes 

 on oaks, stonecrop on the aged branches of trees, and 

 various ferns, especially the polypody. The true epi- 

 phyte, however, is a xerophyte amid vegetation markedly 



