292 MORPHOLOGY OP ANGIOSPERMS 



that no resume of the subject is necessary. Until very recently, 

 the various theories involve the idea that a species is produced 

 as the cumulative result of slight variations through successive 

 generations. In sharp contrast to this De Vries has recently 

 proposed what is called the mutation theory, a brief statement 

 of which may be of service. The experimental work that fur- 

 nishes a substantial basis for the theory was conducted with 

 Angiosperms, and a special student of the group should be pre- 

 pared to recognize any testimony for or against it. A suggest- 

 ive feature of the work of De Vries is his attempt to break 

 away from the speculative method and to subject the problem 

 to experimental investigation. Whether his results indicate a 

 general method of the origin of species in nature or an occa- 

 sional method, or are capable of an entirely different expla- 

 nation and hold no relation to the normal origin of species, 

 remains for future work to determine. In any event, the theory 

 will stimulate investigation and deserves consideration. 



The occasional sudden appearance of what have been called 

 " sports " is well known, but they have not been prominently 

 associated with the origin of species. They have been referred 

 to as cases of " saltatory evolution," and in 1864 Kolliker 

 seems to have been responsible for the term " heterogenesis " 

 as applied to this phenomenon. Quite independently and sim- 

 ultaneously De Vries 11 and Korschinsky 12 have elaborated the 

 same theory as to the origin of species, the former calling it 

 the " mutation theory," the latter using Kb'lliker's name " hete- 

 rogenesis." Korschinsky has brought together a mass of data 

 from the records of gardeners and horticulturists to show that 

 most of the culture " varieties " have arisen through heterogene- 

 sis rather than by selection. De Vries, on the other hand, has 

 experimented extensively with CEnothera Lamarckiana, a spe- 

 cies showing mutability in a high degree. This American spe- 

 cies was found naturalized on an area in Holland about 1875, 

 and afterward spread rapidly. When observed by De Vries, 

 in 1886, two new species were detected among the normal forms, 

 and they have maintained themselves ever since. From 1886 

 until the publication of his book, De Vries made observations 

 upon the naturalized areas and carried on cultures in the botan- 

 ical garden at Amsterdam. As a general result, it may be stated 

 that out of 50,000 seedlings of (E. Lamarckiana 800 were nm- 



