CllAP. V. ROOT-CLIMBEES. 185 



Boot-cUmhers. — ^A good many plants come under this 

 class, and are excellent climbers. One of the most 

 remarkable is the Marcgravia ttmhellata, the stem of 

 which in the tropical forests of South America, as I 

 hear from Mr. Spruce, grows in a curiously flattened 

 manner against the trunks of trees; here and there 

 it puts forth claspers (roots), which adhere to the 

 trunk, and, if the latter be slender, completely embrace 

 it. When this plant has climbed to the light, it pro- 

 duces free branches with rounded stems, clad with sharp- 

 pointed leayes, wonderfully different in appearance from 

 those borne by the stem as long as it remains adherent. 

 This surprising difference in the leaves, I have also 

 observed in a plant of Marcgravia diihia in my hothouse. 

 Eoot-cHmbers, as far as I have seen, namely, the Ivy 

 {Eedera helix), Ficus rejaens, and F. larbatus, have no 

 power of movement, not even from the light to the dark. 

 As previously stated, the Hoya carnosa (Asclepiadaceae) 

 is a spiral twiner, and likewise adheres by rootlets 

 even to a flat waU. The tendril-bearing Bignonia 

 Tweedyana emits roots, which curve half round and 

 adhere to thin sticks. The Tecoma radicans (Big- 

 nomaceae), which is closely allied to many spontane- 

 ously revolving species, climbs by rootlets; never- 

 theless, its young shoots apparently move about more 

 than can be accounted for by the varying action of 

 the light. 



I have not closely obgerved many root-climbers, but 

 can give one curious fact. Ficus repens climbs up 

 a wall just like Ivy ; and when the young rootlets 

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