86 MUTATIONS, VARIATIONS, AND RELATIONSHIPS OF THE OENOTHERAS. 



single cell near the apex of the growing point to undergo such changes during 

 the rapid division that characterizes this region that it gives rise to a mass of 

 cells from which the bud arises, this would favor the probability that the salta- 

 tory changes are due entirely to internal causes and might not be affected at all 

 by circumstances. 



Examples of sports are known in which a section of the shoot involving 

 several branches are of an atypic character. DeVries offers an illustration in 

 his description of a green branch on a colored oak in which the greening not 

 only affected the entire branch, but also a section of the member from which it 

 arose, showing that the mutated protoplast was one which gave rise to more 

 than the atypic branch. In other instances the mutation may involve only a 

 longitudinal section of a branch or of a member or limited growth such as 

 inflorescence, and this may be carried to the extent that even half of a flower 

 may be of an atypic character, and likewise similarly complex fruits may be 

 produced. It is, of course, admissible that in reversionary sports, as most of 

 these sectional variations are, the qualities that appear in the sport are latent 

 in the entire plant and need but a slight stimulus to awaken them, or some 

 force to weaken the dominancy of the main stock. So far as the saltation here 

 is concerned it is one in which any disturbance of the equilibrium would in all 

 probability have but one result. 



In the case of the appearance of characters not inherited in a latent, reces- 

 sive, or active condition, but which constitute a progression or acquisition, the 

 case is different, and if more than one protoplast is concerned in the alterations 

 ensuing preliminary to the organization of a bud-sport, then the suggestion 

 that the alterations were the result of stimulation from factors external to the 

 cell in which the changes ensued would have great force. 



Bud-sports usually occur on the lower part of the main stem, where many 

 of them lie dormant in sleeping buds, and may be awakened by decapitation 

 of the shoot. It is thus to be seen that they belong to a comparatively early 

 stage in the life of the sporophyte. The mutations which give rise to atypical 

 seedlings, on the other hand, seem on theoretical grounds to be due to changes 

 ensuing in the very closing stages of the sporophyte, and previous to the quali- 

 tative or reducing divisions which form the egg, or in the early stages of the 

 pollen mother-cells. Here is encountered a feature not yet recognized in bud- 

 mutations — that of a fairly constant frequency. 



No evidence has yet been secured to show that the pressure or direct action 

 of environmental factors upon the vegetative organs has produced any per- 

 manent inheritable changes in elementary strains of plants. The record of the 

 experiments in which solutions of various kinds were injected into ovaries 

 immediately previous to fertilization seems to point definitely to the con- 

 clusion that the bearers of the hereditary characters may be definitely and 

 directly affected by forces external to the cell, however. The alterations thus 



