MUTANTS 



385 



others will be a little larger or a little smaller, and a very few 

 will be very large or very small. A graph can be made from the 

 results, which shows an even curve, known as Quetlet's (ketlaz) 

 Curve. The phenomenon represented by this curve is known as 

 continuous variation and is seen universally in nature. 



Occasionally, however, sudden changes or discontinuous varia- 

 tions occur. Such was the famous ancon ram which suddenly 

 appeared in 1791 in Massachusetts. This ram had such short 

 legs that it could not jump fences. Hornless cattle, albinos, and 

 the famous beardless wheat found by Mr. 

 Fultz are examples of such variations. 

 These are called mutants or sports. The 

 term mutant has of later years been as- 

 sociated with the Dutch naturalist, Hugo 

 de Vries. Very rarely, as he found, 

 chance mutations appear which breed 

 true. In the evening primrose, for ex- 

 ample, he found eight different muta- 

 tions. This means that new species in 

 nature may arise suddenly, instead of by 

 very slow degrees, as Darwin believed. 

 It is easily seen that such a condition 

 would be of immense value to breeders, 

 as new plants and animals much unlike 

 their parents might thus be formed and 

 perpetuated. About 1910, a bean mutant appeared in the South 

 which was adapted to life in the cotton belt. As a result, more 

 than 6,000,000 acres of these beans were grown in 1917. Mutants 

 have appeared in tobacco, barley, wheat, oats, tomatoes, and 

 potatoes. One of the important parts of the work of the plant 

 breeder is to discover, isolate, and breed useful mutations. 



Selective Planting. — By selective planting we mean choosing 

 the best plants and planting their seeds with a view of improving the 

 yield in some definite particulars. In doing this we must not neces- 

 sarily select the most perfect fruits or grains, but must select seeds 

 from the best plants. Experiments in corn selection at the Uni- 

 versity of Illinois have shown that the oil content of the grain, the 

 starch content, the position of the ear on the plant, and other 



Bearded wheat, and a 

 beardless mutant. 



