THE AFRICAN RUBBER VINES 191 



and 1 to 1^ in. broad, obtusely acuminate at the apex, 

 and acute or subcuneate at the base. The flowers are 

 arranged in dense, compound, axillary and terminal 

 corymbs. 



This vine occurs in German East Africa and Uganda, 

 where it is an important source of rubber. 



Clitandra Arnoldiana, De Wild., which is found in the 

 Belgian Congo, and Clitandra elastica, Chev., occurring in 

 West Africa from the Ivory Coast to Southern Nigeria, 

 are probably varieties of G. orientalis. 



Clitandra henriquesiana, K. Schum. — An erect shrub, 

 up to 6 in. in height, and much branched from the base. 

 The leaves are lanceolate or oblong-lanceolate, obtusely 

 subacuminate, 1 to 2 in. long and | to | in. broad. The 

 flowers are arranged in shortly pedmicled, few-flowered 

 axillary cymes. (See Plate XI.) 



This plant, which occurs in Angola and Northern 

 Rhodesia, is one of the som'ces of root rubber. 



Growth of Rubber Vines. — The majority of the rubber- 

 yielding vines are very slow growers, and in consequence 

 plants raised from seed require a considerable time 

 before they attain a sufficient size for exploitation. The 

 rate of growth is known to vary widely in the different 

 species, but there is little definite information as to the 

 average age at which the various vines can be tapped. 



The results of cultivation experiments in the Belgian 

 Congo indicate that LaTidolphia Klainei, which is one 

 of the quickest-growing vines, may be ready for tapping 

 when about eight years old, whereas it seems probable 

 that the other species of Landolphia and Clitandra in- 

 digenous to the country could not be tapped until they 

 are about fifteen years old. 



Some interesting particulars have been given by 

 Chevalier and others regarding the rate of growth of 

 L. Dawei, which is another quick-growing vine. It 

 is stated that the growth of the seedlings is at first 

 slow, as plants raised in a nursery on good soil only 

 attained a height of 6 in. in six months. Schlechter 

 measured some plants of this species, two and a half 

 years old, which were growing at Soppo in the Cameroons, 

 and found the stems to be 16^ ft. in length, but less than 

 ^ in. in diameter ; whilst Preuss records that specimens 

 at Monte-Cafe in San Thome, when five years old, had 



