TRIPLOIDS 133 



tivated types. Since hyacinths are usually reproduced by 

 bulbs, any particular form can be perpetuated. De Mol 

 has studied the maturation of the germ-cells, both of the 

 normal and the triploid hyacinths (Fig. 80). The normal 

 diploid type has 8 long, 4 medium, and 4 short chromo- 

 somes. The haploid germ-cell contains 4 long, 2 medium, 

 and 2 short chromosomes. Both de Mol and Bellinof have 

 pointed out that the ''normal" may be already a tetra- 

 ploid, since in the reduced group there are two chromo- 

 somes of each size. If so, the so-called triploid may pos- 

 sibly be a double triploid, since it has 12 long, 6 medium, 

 and 6 small chromosomes. 



o' 



a b 



Fig. 81. 



a, Reduced chromosome group of diploid Datura; ft, reduced chro- 

 mosome group of triploid Datura. (After Belling and Blakeslee.) 



Belling has also studied the maturation divisions of a 

 triploid variety of Canna. The chromosomes of each type 

 conjugate in threes. When the chromosomes separate two 

 of each triplet pass as a rule to one pole and one to the 

 other pole, but since the distribution for different triplets 

 is at random only rarely will a diploid and a haploid 

 sister cell result. 



A triploid Datura has been reported by Blakeslee, 

 Belling, and Farnham. It arose from a tetraploid fertil- 

 ized by a normal. The normal diploid type has 24 chromo- 



