66 



THE AMERICAN BOTANIST 



that spring flowers could be found, but I have not been able 

 to take a trip to find out of such is the case. — Edwin D. Hull, 

 The Mutation Theory a Myth. — During the past 

 decade, no phase of botany has received greater attention than 

 the mutation theory of DeVries. In brief, this theory accounts 

 for the origin of new species by the occurrence of sudden leaps 

 or mutations from existing species, in contradistinction to the 

 Darwinian theory which assumes a slower and more gradual 

 variation from existing forms. Both theories are based on the 

 idea that plants vary from the normal and differ chiefly in the 

 length and number of the jumps or mutations required to make 

 the new form a species. DeVries stands for a single long 

 jump, Darwin for a succession of shorter ones. Much plausi- 

 bility has been given the theory advocated by DeV/ries by his 

 production of new forms from that form of evening primrose 

 known as Oenothera Lamarckiana but Prof E. C. Jeffrey 

 writing recently in Science claims that 0. Lamarckiana is a 

 hybrid. The great trouble is to decide what are and what are 

 not hybrids. The old test for a hybrid w^as its sterility. If 

 completely sterile it was considered as certainly a hybrid. Hy- 

 brids, however, are now known to be of various grades of fer- 

 tility. A great number of crosses between different species 

 have been made and as the plants crossed differ in the degree 

 of relationship, it follows that various grades of sterility may 

 exist. Jeffrey gives it as his opinion that hybrids may always 

 be identified by the fact that the pollen grains are more or less 

 abortive and infertile. Judged by this test, the plant with 

 which DeVries made most of his experiments is a hybrid and 

 Jeffrey insists that in consequence the mutation theory has no 

 standing in court and should be relegated to the realm of 

 myths. It may be said, however, regardless of the merits of 

 the new theory, that the discussion of the subject has had a 

 tremendous influence on the production of new forms by breed- 

 ers and this much at least must be set down to its credit. 



