CHAPTER XII 



FLAX AND TOBACCO 



FLAX 



Flax has been reported to have been grown by the Lake 

 Dwellers of Switzerland as early as 4,000 to 2,000 years 

 B.C. (Chapter I). Although the Egyptians and Hebrews used 

 flax to make clothing in very ancient times, little is known of the 

 origin of our present cultivated varieties. 



Species Crosses. Tammes (1911, 1915, 1916) has made some 

 interesting genetic studies of flax species crosses. Reciprocal 

 crosses were made between cultivated varieties of Linum usitatis- 

 simum and the wild species L. perenne, austriacum, narbonnenese, 

 grandifiorum, and angustifolium. No seeds capable of germinat- 

 ing were obtained except in the angustifolium cross. This was 

 considered a good cause for believing thatL. angustifolium has the 

 best right of any of the wild species to be considered the ancestral 

 form of cultivated flax. This wild species differs from the common 

 cultivated varieties in that the seeds and capsules are smaller, the 

 edges of the partition walls of the capsule are hairy, and the capsules 

 open at maturity. In general, crosses between hairy and glabrous 

 races showed dominance of the hairy condition in FI and a segre- 

 gation of 3 hairy to 1 glabrous in F 2 . The open type of capsule 

 was imperfectly dominant in F\ t i.e., the capsules did not open 

 as widely as in the open parent. Segregation occurred in F 2 . 

 Parental types, i.e., homozygous open and homozygous closed 

 lines, were produced in later generations. Three or four factors 

 were necessary to explain results. 



Interrelation of Factors for Flower and Seed-Colors. Care- 

 ful studies have been made of the interrelation in inheritance 

 of various flax characters (Tammes 1911, 1914, 1915, 1916). 

 The results were carefully analyzed. Three factors called A, B, 

 and C, were shown to be necessary for the production of dark 

 blue flowers. B and C together produce light blue flowers, and 

 A is an intensification factor which in the presence of B and C 

 produces dark blue flowers. When C is homozygous in the pre- 

 sence of B, the veins of the petal are darker than the rest of 

 the petal. The veins are the same color as the rest of the petal 

 when C is heterozygous in the presence of B, B and A give the 



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