342 



WILD AND CULTIVATED COTTONS 



Union of 



similar 



gametes. 



Ascertain- 

 ment of 

 stability. 



Purity of 

 strain. 



Pollen, 

 grains. 



' field selection,' were their production attempted by systematic hybridi- 

 sation in place of the present method of accidental elimination. 



This view might be exemplified again and again. Mr. W. Bateson 

 for example (see his address at the New York Hybrid Conference), 

 made the significant observation, ' We have lost for ever, I think, 

 the conception that fixity of character is solely or chiefly a function 

 of the number of generations during which that character has been 

 manifested, or of the number of successive selections of that particular 

 variety which has been made.' 



'Purity of strain, or fixity of character, is, on the contrary, 

 due primarily to the union of similar gametes in fertilisation.' 

 Conversely when dissimilar gametes are crossed the resultant 

 is the reappearance of an ancient form (see pp. Ill, 134). 



It is thus obvious that ' field selection ' may often be a useless 

 expenditure of time and money, a process of groping in the dark, 

 due to being concentrated more frequently on unstable than stable 

 objects. The failures are infinite and soon forgotten, the successes 

 are few, but instantly seized upon and preserved. It is imperative 

 that the first principle in selection should be the ascertainment 

 of stability. Accurate knowledge of the species or variety, as 

 recognised by botanists, is in many instances at least the first and 

 most important step in that direction. But the study involved may 

 call forth investigations ordinarily deemed beyond the sphere of the 

 systematist. The colour of the flower, the degree of segmentation 

 of the leaves, the union of the bracteoles, the length, colour and texture 

 of the floss, or the shape and size of the pollen-grains, may each 

 and all afford characters by which to test the purity or otherwise 

 of the strain present in the plant under observation and experiment. 

 Characters which in systematic botany might be regarded as too 

 trivial for consideration may accordingly assume importance in this 

 special study. It is on this account that I have been induced 

 to place value on certain observations made into the condition of the 

 pollen-grains. But while most anxious to avoid raising false 

 expectations, it would seem to me that the pollen-grains may 

 sometimes afford useful hints as to the hybridisation that has 

 been accomplished, or which may be accepted as actually existing 

 in desirable and useful stocks. With that object in view I 

 venture to set forth some of my studies, though fully conscious 

 that more extended investigations will be necessary before these 

 can be definitely accepted. 



