HETEROPLOIDS 189 



De Vries identifies six trisomic mutant types, and a 

 seventh one, also, that differs genetically more strikingly 

 from the other six than they do from each other. These 

 seven trisomic types may, he suggests, correspond to the 

 seven chromosomes of the evening primrose. A list of six 

 of them is given below. A diagram of the corresponding 

 chromosome groups is given in Fig. 107. 



15-chromosome mutants. 



1. Lata group. 



a. Semi-lata. 



b. Sesquiplex mutants: albida, flava, delata. 



c. Subovata, sublinearis. 



2. Scintillans group. 



a. Sesquiplex mutants: oblonga, aurita, auricula, 



nitens, distans. 



b. Diluta, militaris, venusta. 



3. Cana group : candicans. 



■4. Pallescens group : lactuca. 



5. Liquida. 



6. Spathulata. 



This list of six 15-chromosome primary mutants in- 

 cludes some secondary mutant types arranged under 

 their primaries. Their interrelations are shown not only 

 by similarities in characters, but also by the frequency 

 with which one throws the other. Two of them, albida and 

 oblonga, have two kinds of eggs but only one kind of pol- 

 len, and are called one-and-one-half or sesquiplex mu- 

 tants. Another secondary, candicans, is also a sesquiplex 

 type. The central or largest ' ' chromosome ' ' of the group 

 (Fig 107) carries the "factors" for velutina or for those 

 of laeta. De Vries assigns to them also, from evidence 

 found by Skull, the new mutants funif&lia and perrivens. 

 It may seem probable, therefore, following Shull, that 



