Xo. 55S] SHORTER ARTICLES AND DISCUSSION 



377 



from variegated ones as here outlined 5 bears more than a super- 

 ficial resemblance to mutation. The comparative frequency of 

 the change in factors from V to 8 in variegated plants is per- 

 haps the most striking dissimilarity between the two. Muta- 

 tions must certainly result from the loss or gain or the modifica- 

 tion of genetic factors. They must arise potentially whenever 

 a change in genetic factors takes place, whether in the somatic 

 cells or germ cells of the parent or in the early somatic cells of 

 the mutant offspring. It is conceivable that many mutations 

 may arise in a manner similar to the origin of red-eared maize 

 plants from the male gametes of variegated maize — similar in the 

 sense that the change in genetic factors may occur in somatic 

 cells without any visible modification of those cells or of any 

 part of the plant body arising from them. 



East has shown (loc. tit.) that Mendelian characters of potato 

 tubers sometimes arise as bud-variations. If the same charac- 

 ters should be found to appear as seed-sports, that fact would 

 not, in some cases at least, preclude the possibility of their 

 having had their potential origin in somatic cells of the parent 

 plant. If a change of genetic factors having to do with tuber 

 shape should occur in the growing point of an underground 

 stem, the change would doubtless manifest itself in any tubers 

 that grew from the modified cells of that stem (provided that 

 the new character were a dominant one or that the change 

 affected both of the like genetic factors of the modified cells) 

 and the change would at once be recognized as a bud-sport. 

 But if exactly the same change should occur in the growing 

 point of an aerial stem, the new tuber shape obviously could not 

 manifest itself in the parent plant and would appear, if at all, 

 only among the seedlings of that plant where it would of course 

 be classed as a "seed-sport." 



Whether or not mutations do arise as suggested here, the pos- 

 sibility seems great enough to warrant the extension of experi- 

 ments in their artificial production to include the treatment not 

 merely of plant ovaries but of all growing parts from which 

 gametes may be expected eventually to arise. In animals of 

 course treatment would have to be aimed at the germinal tissue 

 but with the higher plants in general almost any meristematic 

 tissue is potentially germinal tisue. 



K. A. Emlrson 



r-sporting variation, are to be interp 

 "Species and Varieties," pp. 315-321 



