249 



Selection in vegetative propagation is also of assistance in 

 producing a healthy strain of plants. Webber gives an account of 

 experiments with the Ripley Queen pine-apple, which is liable to a 



disease which causes it to 'go lilind.' that is. advance to the end of 

 its growing period and sucker from below without fruiting. The 

 experiment consisted in planting in one bed suckers from diseased 

 plants and in an adjoining bed suckers from apparently healthy plant-. 

 In the former bed, eighteen months later, he found that <>.'> per cent, 

 had contracted the disease, while in the other beds slightly les» than 

 4 per cent, showed the disease. This being the result of but one 

 selection, it would seem probable that the disease might be 

 completely controlled by a continuous selection of suckers from 

 healthy plants. 



Another interesting illustration of the modifications obtained by 

 the careful and continued selection of vegetative parts — one of 

 particular interest in West Indian agriculture— is the breeding out of 

 thorns from citrus trees by bud selection. To quote again from 

 Mr. Webber's article : ' Seedling oranges and lemons are almost 

 invariably very thorny, but nevertheless the majority of the standard 

 varieties cultivated are now largely thornless, owing, it is said, to the 

 continuous selection of buds from thornless branches. According to 

 the testimony of orange nursery -men, it is quite certain that thorns 

 can be bred out in this w r ay in every case, and usually to do so 

 requires but three or four bud generations. It is probable, in the 

 case of other fruit trees, that by selecting buds or cuttings from 

 branches that are thornless, or which have fewer thorns than usual, 

 the thorns could be entirely bred out, or at least the greater number 

 reduced. 



Writing in the Bulletin of the Botanical Department of Jamaica 

 for November 1900 on the subject of budding orange trees, Mr. W. 

 Cradwick says : " Buds with thorns attached should not be used ; 

 they do not grow so readily, and, if they grow, result in a tree on 

 which long thorns will be one of the chief features. A tree grown at 

 Hope from a bud with thorns \\ inches in length attached to it 

 produced thorns over 8 inches in length." 



In this connexion it may be useful to review briefly the interest- 

 ing series of experiments in the chemical selection of sugar-cane 

 conducted by Dr. Watts at Antigua : — 



' The object of the experiment is fr ascertain whether the sac- 

 charine content of the sugar-cane can be effected by selection of 

 cuttings.' These experiments consist in selecting tAvo series of canes 

 canes— (1) canes rich in sucrose, called ' High' canes, and (2) canes 

 poor in sucrose, called ' Low' canes. The experiments have now been 

 in progress for four years. Each year the ten richest caries have 

 been selected from the ' high' plot and the ten poorest from the ' low ' 

 plot. This represents an attempt to obtain two divergent series — 

 ' one tending to increased richness, and the other to decreased rich- 

 ness.' In making the selection, the canes are examined by cutting off 

 the basal portion in the middle of the fifth internode from the base, 

 crushing this basal portion in the Chatanoga mill, and determining 

 the amount of sugar by means of the polariscope in the sample of 

 juice so obtained. 



