32 INTRODUCTION. 



not only to show segregation in many of the characters, but also 

 to isolate forms resembling the parents as well as some new 

 constant forms differing from either parent. 



The most thorough examination of the inheritance of 

 characters connected with the size of organs are the investiga- 

 tions of Tammes^ on the length and breadth of the seed and 

 the length and breadth of the petal in Linum. The size of the 

 seed was found to be practicalh^ unaffected b}^ the environment 

 and therefore formed very suitable material for such work. The 

 limits of variation and the co-efficient of variability were care- 

 fully determined for each parent. It was found that while the Fi 

 generation was intermediate between the parents, the second 

 generation could not be separated into groups, but formed a 

 continuous series, and that, in manj^ cases, no individuals could 

 be found which resembled the parents. In the F3 generation 

 no individuals breeding true or resembling either parent could 

 be found but the limits of variation were smaller than in the 

 Fo and differed in each case, the combined variation covering the 

 limit of variation of the F2 generation. These results point to 

 the existence of several factors with segregation. The various 

 intermediate heterozygotic forms would naturally contain fewer 

 heterozygotes than the Fj generation, and would therefore vary 

 within smaller limits. 



East and Hayes,- in 191 1, published similar results on size 

 characters in maize, such as height of the plant, length of cobs, 

 weight and size of seeds, but in most cases the investigations 

 were not taken beyond the second generation. 



Three investigations on the characters connected with the 

 size of tlie organs in tobacco have been published, but in no case 

 have the investigations been carried beyond the second gener- 

 ation. Lock,' in 1909, published a preliminary note of some 

 species crosses in the genus Nicoliana, the characters considered 



* Taminos, I.e. 



* East and Hayes. Bnllelin Ku, Connecticut Agriciilliiml E:vperimenl Station. I'.tl 1. 



* Lock, Anval/i Royal Botanic Gardens, Peradcniya, Vol. IV, 190i). 



