SAPROPHYTES IX WATER, ON THE BARK OF TREES, A>.1) oX ROCKS. 107 



always seen torn oft' with the rliizoids at the places where they issue from the 

 stemlets. The same thing occurs in the case of the roots of tropical oi'chids 

 gi'owing to the tree-trunks which constitute their habitat. The majority of these 

 tree-orchids nestle, no doubt, in mould-filled crevices of the bark, and nourish them- 



Fig. 15.— Aerial Roots of a Tropical Orchid {Sarcanthits rostratun) assuming the form of straps. 



selves, besides, by means of special aerial roots whicii hang down in white ropes 

 and threads, like a mane, from the places where the plants are situated upon the 

 trees, and which will pi-esently be described in detail. But a small section develops 

 strap-shaped roots as well, which adhere finnly to the bark with their flat surfaces. 

 This phenomenon is most strikingly exhiliited bj- the splendid Phakcnopsis 



