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THE AMERICAN NATURALIST [Vol. XLIX 



all of its species. Others suggest that the more chromo- 

 somes a plant species possesses the greater is its varia- 

 bility. Thus Spillman 3 speaks of the low variability of 

 rye, suggesting its small chromosome number (six or 

 eight) as a possible reason; for maize, having probably 

 from twenty to twenty-four chromosomes, is infinitely 

 more variable than rye. However, Britton's "Manual" 

 selects Crepis virens for special mention as an extremely 

 variable species from among the four or five other species 

 listed under that genus, and it is known that C. virens 

 has only six chromosomes, while three other species of 

 Crepis investigated all have higher numbers. Again, ac- 

 cording to Wiegand, the Carina has only six chromosomes, 

 yet every gardener is well acquainted with the infinite 

 variety in Cannas. 



The Chkomosomes and Variability 

 After a consideration of the above facts, one may well 

 hesitate to state that there is even a high degree of corre- 

 lation either between variability in chromosome number 

 and general variability, or between high numbers of chro- 

 mosomes and a high degree of variability in specific char- 

 acters. On the other hand, it is not certain that the data 

 upon which our discussion is based are relevant to the case 

 in hand. We have discussed a possible relationship be- 

 tween chromosome numbers and species complexity and 

 variability as found in the wild. This is not at all the 

 same thing as discussing the relationship between chro- 

 mosome number and true variability. It is true that com- 

 plexity and specialization of plants and animals seem to 

 have no connection with chromosome number, and that 

 within a family a genus or a species profusion of taxo- 

 nomic characters do not go hand-in-hand with high chro- 

 mosome numbers. But in these cases our data come from 

 persistent forms. What the actual inherent variability 

 of the protoplasm is in most cases we do not know. Dro- 

 sophila ampelophila, a species with only four chromo- 



3 Six according to Westgate's unpublished data; eight according to Xakao. 



