206 TROPICAL AGRICULTURE CHAP, ix 



Transverse When the vines have reached the tops of the trees or other 



supports. supports, bamboos may be fixed horizontally from tree to tree 



or post to post, and the vines trained along them. The trees 



must be kept down low so that the vines do not get out of 



reach, and the branches must be judiciously lopped in order 



Manures. to prevent too much shade. No animal or artificial manures 



should be used, but rotten leaves and vegetable soil may be 



applied to the roots after each crop is gathered. 



Crops in the FERTILISATION OF THE FLOWERS. The plants will COm- 



year ' mence to flower in the second year after planting, and full 



crops may be expected in the fourth year. In Central and 



South America, where the orchid grows wild, fertilisation of 



the flowers is effected by means of insects or other agency. 



Artificial The parts of the flower are so arranged that self-pollination 



fertilisation . 



essential. is impossible ; and, therefore, it must be effected by some 

 foreign agency. It is usually said that this agency is an 

 insect one, but none of the writers on the vanilla give any 

 description of the insect or any particulars regarding it. The 

 author of this book once gathered a few vanilla pods from 

 vines growing in his garden in Dominica, and as none of the 

 Fertilisation flowers were artificially fertilised that year it is probable that 

 bu-ds Ummmg pollination was effected by humming birds, which were 

 frequently seen to insert their long beaks into the flower for 

 the purpose of extracting the nectar. It is likely, therefore, 

 that birds may have as much to do with fertilisation of the 

 vanilla orchid as insects. In the cultivation of the plant, 

 however, it will not do to depend on such precarious 

 agencies, and the planter, in order to ensure crops, must 

 fertilise the plants himself. 



Description The flower of the vanilla orchid is very different from the 

 flowefs tyP 6 of nower described in the first part of this book ; but, 

 on examining it carefully, the outer floral envelope, consist- 

 ing of three sepals, and the inner one, consisting of three 

 petals, may be made out. The lowest of the petals is very 

 different from the others ; it is called the labellutn, or lip, 



