208 



TROPICAL AGRICULTURE 



CHAP. 



Two obsta- 

 cles to self- 

 fertilisation. 



Artificial 

 fertilisation, 

 how accom- 

 plished. 



The flower- 

 ing season. 



and it envelopes the columnar continuation of the axis of 

 the plant onwhich a.re set the curious anther and stigma. 

 This continuation is called the column, and it and the 

 other parts of the flower are shown in the foregoing 

 wood-cuts. At the top of the column is a hood which covers 

 up the anther and pollen masses, and below this is the 

 viscid stigmatic surface, protected and hidden by a project- 

 ing lip sometimes called the lamellum. Thus we see that the 

 pollen is shut in by the hood, and the stigma is shut in by 

 the lamellum, so that two obstacles prevent self-pollination. 

 The object of artificial fertilisation is to remove these ob- 

 stacles, and to permit the pollen masses to approach the 

 stigma. This is easily effected, firstly, by detaching the hood, 

 which is accomplished easily by touching it lightly with a 

 piece of sharpened wood ; secondly, by slipping the lamellum 

 under the anther ; and, thirdly, by ensuring contact of the 

 pollen and stigma by gentle pressure between the thumb 

 and forefinger. The operation is performed in a few seconds 

 after a little practice, and it may be facilitated by holding 

 the column between the thumb and middle finger of the left 

 hand, whilst it is supported at the back with the forefinger ; 

 the right hand is then free to use the fertilising instrument, 

 which should be rather blunt and flattened at the end. A 

 tooth broken from an old comb, and fixed into a piece of thin 

 bamboo a few inches in length, has been used by the author 

 in fertilising many vanilla flowers. 



CROPS. If the fertilising operation prove successful, the 

 flower will gradually wither whilst the pod will grow rapidly. 

 If unsuccessful the flower will fall off before the second day, 

 and the ovary will remain undeveloped, turn yellow, shrivel 

 up, and drop off the stalk. 



The flowers come out in February and March in clusters 

 of from ten to twenty, but not more than half a dozen of the 

 cluster should be fertilised ; and, in this way, fine large pods 



