POLYPLOID SERIES 157 



moved to one or the other pole ; some reach the poles un- 

 divided, others split and the halves move to the poles. 

 Not infrequently 7 single chromosomes are left in the 

 middle plane between the two polar groups (Fig. 90i). 

 Three counts are given in the following table : 



At the second division 11 or 12 chromosomes are, as a 

 rule, present; some are doubles (split lengthwise), others 

 singles. The former divide normally, the daughter chro- 

 mosomes going to one or the other pole; the singles are 

 distributed without division to one or the other pole. 



From this evidence it is not possible to determine 

 which chromosomes conjugate in the hybrids. Since the 

 number of gemini does not exceed 7, these may be inter- 

 preted as the result of union of the 14 chromosomes of 

 the Emmer parent, or as the result of the union of 7 of 

 the Einkorn with 7 of the Emmer chromosomes. 



In a few crosses between Emmer and Vulgare, fertile 

 hybrids have been obtained. Kihara has studied the chro- 

 mosomes in the maturation division of some of the F 3 , F 4 , 

 and later generations. The chromosome numbers in the 

 plants vary and there are irregularities in the distribu- 

 tion of some of them during maturation, leading to fur- 

 ther irregularities, or to the reestablishment of a stable 

 type like one of the original types, etc. These results, 

 important for the genetic study of the hybrids, are too 

 complex for our present purpose. 



Kihara studied hybrids (one combination) between a 

 Vulgare wheat and a race of rye, the former having 42 

 chromosomes (n=21), the latter 14 chromosomes (n= 

 7). The hybrid (with 28 chromosomes) may be called a 



