Mutations in Cultivation. 197 



I have already said that the so-called cases of atavism, 

 brought forward as evidence against this constancy, are 

 really cases of crossing. The copper beech illustrates 

 this well. Its distinguishing character is reported as be- 

 ing inherited to a highly variable extent, according to 

 the locality in which it lives. Sometimes all the seeds 

 come true; sometimes only 20%. But as the trees in 

 question grow amongst ordinary beeches, and as arti- 

 ficial fertilization is of course out of the question, they 

 must usually be fertilized by pollen from the surround- 

 ing trees. If we want to draw any conclusions from 

 the posterity of a copper beech w^e must confine our atten- 

 tion to properly isolated trees. 



In conclusion we may refer to the familiar fact that 

 in cultivation mutations follow on one another so that 

 the plant gradually becomes separated from the original 

 form by an increasing number of characters; which is 

 exactly what, in all probability, occurs in nature. The 

 great number of long names of garden plants is evidence 

 of this ; as for example Scabiosa atropiirpurea nana pur- 

 purea from which a Forma carnca and a Forma rosea 

 have subsequently arisen ; Calliopsis tinctoria pumila pur- 

 purea, Tagetes potula nana with dark leaves, and another 

 form of this dwarf with bright yellow flowers and so 

 forth. The succession of names often indicates the stages 

 of development of the form in their historical sequence. 



Finally, then, we may say that a gradual origin of 

 elementary species has not yet been observed ; but that 

 there are hosts of instances in which new ''species" have 

 arisen suddenly or in which at least such an origin is in 

 the ver}^ highest degree probable. Scarcely ever has the 

 new form been isolated immediately it appeared : it is 

 usually left like its parents to pollination by insects. So 



