DEPARTMENT OF GENETICS. 



105 



different offspring all possible combinations of sets with 2 and with 3 chromo- 

 somes. Apparently differential viability and other factors prevent a close 

 approximation to the laws of chance and we are getting in our triploid off- 

 spring many diploids, the common simple trisomic mutants and a considera- 



Balanced types 



Unbalanced types 



Diploid 



-vv— 



Modified diploids 



y-^- 



II -> 



Simple tetrasomic 



^/ 



II 



S^ 



Simple tnsomic 



— vvJ 



/ 



Double trisomic. 



Triploid 



^iii<^ 



Tetraploid 



#1111.^ 



•# iiir^ 



Modified tetraploids 



Simple hexasomic 



# Itil % 



Simple pentasomic 



^'•'14* 



# 111'! '^• 



Simple trisomic 



Fig. 1. 



Table 1. — Chromosomal types of mutants in the jimson weed (Datura stramonium). 



The somatic number of chromosomes is given in parentheses after each type. 



B.\LANCED Types (12n): Diploids (Normal) (24); Triploids (36); Tetraploids (48). 

 Unbalanced Types (12n+a;): 

 Modified diploids (24 +a;). 



A. Simple trisomic (24+x): 1, Globe; 2, Poinsettia; 2a, P. var. Wiry; 3, Cocklebur; 



4, Ilex; 5, Mutilated; 6, Sugar-loaf; 7, Rolled; 8, Reduced; 9, Buckling; 10, Glossy; 

 11, Microcarpic; 12, Spinach. 



B. Simple tetrasomic (24+2, the 2 extras in the same set): 1, Round-leaf Globe. 



C. Double trisomic (24+1 + 1, one extra in each of 2 different sets): 1, Ilex-Buck- 



ling (?) and a number of other double mutants not yet analyzed by breeding tests. 

 Modified tetraploids (48 +x). 



A. Simple pentasomic (48 + 1) : 1, Globe; 2, Poinsettia; 3, Cocklebur; 4, Ilex; 5, Rolled; 



6, Reduced; 7, Glossy; 8, Microcarpic. 



B. Simple hexasomic (48+2, the 2 extras in the same set): 1, Globe. 



C. Simple trisomic (48-1, a single deficiency in one set). 



