60 cross-kkrtilisation in tiik indian cottons. 



Concluding observations. 

 Siiffiiiont has here been shown to warrant two main conclu- 

 sions, firstly, that a considorable dogrec of sterility results from self- 

 fertilisation repeated through a number of successive generations ; 

 and, secondly, that cross-fertilisation takes place to a considerable 

 extent, though the greater portion of this is limited to neighbouring 

 plants. 



The practical bearing of these considerations is of some import- 

 ance. In the early stages of experimental work, when individual 

 plants are under examination, it is necessary to guard against the 

 effects of cross-fertilisation by protecting the flowers. By so doing, 

 however, considerable danger is incurred of the loss of vigour and 

 even of the loss of the race through sterility. While, therefore, 

 it is not impossible to raise and carry on single plant cultures — and 

 in fact, such has actually been accomplished in the case of most of 

 the types, — such cultures are likely to be of slight practical value- 

 As far as possible, therefore, it appears advisable to avoid such cul- 

 tures and to rely for purity on the careful selection, combined with 

 roguing, among such plants as are least likely to have been crossed. 

 For this purpose the types must be grown in numbers sufficient to 

 give a fair body of individuals separated by at least 10ft. and by in- 

 tervening plants from individuals of a different type. In this man- 

 ner a race of Type 7 exhibiting the full vigour of the original stock 

 has been raised. A further method has been attempted in which a 

 set of 40-50 plants of one type have been enclosed by a single 

 net. It is here impossible to exclude all insects, but the number 

 passing through the net is very small, while those enclosed arc 

 only able to effect cross-fertihsation between individuals of the 

 same type. The effectiveness of the method still remains to be 

 proved. 



It has been sliowii that, in exceptional cases only, is the cotton 

 crop in any part of India piu'e and the same may be said to be the 

 case in other countries also. A series of cottons grown from seed 

 from China and Persia have been found to consist of a number of 



