MUTATIONS 115 



part promptly exterminated by the rigors of natural selection, 

 which therefore could not have been the chief agency in their 

 creation. 



Accordingly he conceived the idea of cultivating a few unstable 

 forms under conditions such as would protect and preserve any 

 mutations that might arise, hoping jn this way to throw some 

 light on the origin of new types and to determine whether in the 

 origin of species natural selection works principally upon indi- 

 viduals or upon types. 



Experiments with toadflax 1 (Linaria vulgaris). These experi- 

 ments were designed to test the origin of the peloric form. 2 The 

 toadflax was chosen, first because the peloric form is known to 

 have arisen repeatedly, and second because the change involved 

 is slight, structurally speaking. These two considerations gave 

 reason for the hope that if the species were put under careful 

 observation and control, he (De Vries) "might be present at the 

 time when nature produces another of these rare changes." 



The experiments commenced in 1886 with normal plants bear- 

 ing "one or two peloric flowers," as is common with most indi- 

 viduals of this genus. The roots were planted in the garden, 

 and flowered and seeded in 1887. This second generation was 

 grown for three years, producing in 1 889 3 one, and in 1890 two, 

 peloric structures. The seeds of these were saved and produced 

 the third generation in 1890-1891. Among some thousands of 

 blossoms in this generation there was one five-spurred flower. 

 This was pollinated by hand and luckily produced " abundant 

 fruit, with enough seeds for the entire culture of 1892, and they 

 only were sown." 4 



1 De Vries, Species and Varieties, etc., pp. 464-487. 



2 The normal flowers of the toadflax are exceedingly unsymmetrical. Aside 

 from bearing a short spur, they are described as consisting of a " two-lipped corolla, 

 the lower lips spreading and three-lobed, with a base so enlarged as to nearly 

 close the throat." Plants bearing such unsymmetrical flowers as do toadflax, snap- 

 dragon, etc., are known occasionally to produce peloric, that is, symmetrical, 

 flowers. Not only that, but peloric varieties are not unknown, and these experi- 

 ments were designed to solve the manner of their origin. 



3 The toadflax is a biennial. 



4 Peloric flowers of this species are commonly sterile, but in any case are 

 dependent upon artificial fertilization. They are by nature ill adapted to preserve 

 themselves. 



