152 THE THEORY OF THE GENE 



(1921), to the Neolithic period in Europe. Another type, 

 the Emmer group, with 28 chromosomes, was grown in 

 Europe in prehistoric times, and in Egypt as early as 

 5400 b.c. It was later supplanted in the Graeco Roman 

 period by wheat with 28 chromosomes, and by one with 

 42 chromosomes of the Vulgare group (Fig. 88). The 

 number of varieties is greatest in the Emmer group, but 

 there are more different "forms" in the Vulgare group. 

 The chromosomes have been studied by several investi- 

 gators. The most recent work is that of Sakamura (1900) 

 and Kihara (1918, 1924) and Sax (1922). The follow- 

 ing account is taken largely from Kihara 's monograph 

 and to some extent also from Sax's papers. The next 

 table gives the observed diploid number of chromosomes 

 and the observed or estimated haploid number. 



Haploid Diploid 



Einkorn group, Triticum monococcum 7 14 



Einkorn group, Triticum dicoccum 14 28 



Einkorn group, Triticum polonicum 14 28 



Emmer group, Triticum durum 14 28 



Emmer group, Triticum turgidum 14 28 



Vulgare group, Triticum Spelta 21 42 



Vulgare group, Triticum compactum 21 42 



Vulgare group, Triticum vulgare 21 42 



The haploid groups are represented in Fig. 88a (mo- 

 nococcum), Fig. 88e (durum), and Fig. 88h (vulgare). 



The normal maturation of a member of each of these 

 groups is shown in Fig. 89 from Sax. In the Einkorn 

 wheat the seven gemini (conjugated chromosomes) divide 

 at the first division, seven going to each pole. There are 

 no lagging chromosomes. At the second division of each 

 daughter cell the seven chromosomes split into daughter 

 halves. Seven go to each pole. In the Emmer type the 14 

 gemini divide at the first maturation stage. Fourteen 

 chromosomes go to each pole. At the second division each 



