Elementary Species in Nature 59 



portance. Among the range of elementary spe- 

 cies those should be used which not only pos- 

 sess the desired advantages in the highest de- 

 gree, but which promise the best results in other 

 respects or their earliest attainment. The 

 fuller our knowledge of the elementary species 

 constituting the systematic groups, the easier 

 and the more reliable will be the choice for the 

 breeder. Many Californian wild flowers with 

 bright colors seem to consist of large numbers 

 of constant elementary forms, as for instance, 

 the lilies, godetias, eschscholtias and others. 

 They have been brought into cultivation many 

 times, but the minutest distinction of their ele- 

 mentary forms is required to attain the highest 

 success. 



In concluding, I will point out a very interest- 

 ing difficulty, which in some cases impedes the 

 clear understanding of elementary species. It 

 is the lack of self-fertilization. It occurs in 

 widely distant families, but has a special inter- 

 est for us in two genera, which are generally 

 known as very polymorphous groups. 



One of them is the hawkweed or Hieracium, 

 and the other is the dandelion or Taraxacum 

 officinale. Hawkweeds are known as a genus 

 in which the delimitation of the species is al- 

 most impossible. Thousands of forms may be 

 cultivated side by side in botanical gardens, ex- 



