I22 VARIATION 



happened, rather than to enter just afterward and only in time 

 to note results with no evidence as to methods. 



Of all the hundreds of plants cultivated he found the evening 

 primrose most fertile in distinct strains, both in the wild and 

 hi the cultivated state. Other species gave rise to varieties 

 freely, but no other appeared to be sufficiently mutable to give 

 rise freely to what he regarded as elementary species. 



Of all the primroses, CEnothera Lamarckiana, commonly called 

 Lamarck's evening primrose, was the most prolific in distinct 

 forms, and accordingly this was chosen by De Vries for special 

 attention in his experiments. It is described as "a stately 

 plant with a stout stem, attaining often a height of 1.6 m. or 

 more. When not crowded, the main stem is surrounded by a 

 large circle of smaller branches growing upward from its base 

 so as to form a dense bush. These branches in their turn have 

 numerous lateral branches. ... Contrary to their congeners, 

 they are dependent on visiting insects for pollination." 



Ordinarily this primrose is a biennial, producing rosettes in 

 the first year and stems in the second year. Both the rosettes 

 and the stems are highly variable in nature, producing a num- 

 ber of distinct races, some of which show a marked ability to 

 hold their own under natural surroundings, while others -are too 

 weak to endure. 



Many of these De Vries regarded as new species. Experi- 

 ments to determine this point were commenced with stock dis- 

 covered near Hilversum, and three plans were followed : first, to 

 transplant the apparent new species into the garden whenever 

 the new race was sufficiently strong; second, to reproduce weak 

 races by sowing seeds from " indifferent " plants growing wild ; 

 third, to sow the seeds from the introduced plants. " These 

 various methods," he adds, "have led to the discovery of over 

 a dozen new types never previously observed or described." 



These new plants are divisible, according to De Vries, into 

 five different heads or " groups " : (i) those that " are evidently 

 to be considered as varieties in the narrower sense of the 

 word," representing retrograde development ; (2) " progressive 

 elementary species " which are " as strong as the parent 

 species " ; (3) " progressive elementary species," but weaker than 



