Elementary Species in Nature 55 



can only be recognized by comparative experi- 

 mental studies. 



Though the evidence already given might be 

 esteemed to be sufficient for our purpose, I 

 should like to introduce a few more examples; 

 two of them pertain to American plants. 



The Ipecac spurge or Euphorbia Ipecacu- 

 anha occurs from Connecticut to Florida, 

 mainly near the coast, preferring dry and sandy 

 soil. It is often found by the roadsides. Ac- 

 cording to Britton and Brown's "Illustrated 

 Flora " it is glabrous or pubescent, with several 

 or many stems, ascending or nearly erect ; with 

 green or red leaves, which are wonderfully 

 variable in outline, from linear to orbicular, 

 mostly opposite, the upper sometimes whorled, 

 the lower often alternate. The glands of the 

 involucres are elliptic or oblong, and even the 

 seeds vary in shape. 



Such a wide range of variability evidently 

 points to the existence of some minor types. 

 Dr. John Harshberger has made a study of 

 those which occur in the vicinity of Whitings in 

 New Jersey. His types agree with the descrip- 

 tion given above. Others were gathered by 

 him at Brown's Mills in the pinelands. New 

 Jersey, where they grew in almost pure sand in 

 the bright sunlight. He observed still other 

 differentiating characters. The amount of seed 



