MUTATIONS 



125 



transmitted to a portion only of its offspring, thus behaving like 

 hybrids. Indeed, he specifies that " on the average one fourth 

 of the offspring are lata" the others assuming the character of 

 the pollen parent," a strict example of hybridism between a 

 weaker and a stronger form, according to Mendel's law. 



Group (5), inconstant forms : 



O. scintillans is a perfectly fertile form, bearing smooth, dark- 

 green leaves with glistening surfaces. It is a natural dwarf, 

 easily cultivated as an annual. When fertilized with its own 

 pollen to produce a " pure " strain, it is found that the seedlings 

 all resemble the parent, but that soon afterward they diverge 

 into various types. Some of these resemble the original parent 

 stock (Lamarckiana) and others remain pure, but the proportion 

 is very variable. These might be regarded as simple reversions, 

 except that occasionally other types appear, especially oblonga, 

 lata, and nanella, the first often constituting 10 per cent of the 

 sowings. It thus shows a disposition to give rise to the same 

 distinct forms as does its own parent, and is thus regarded by 

 De Vries as being itself in a " highly mutable state." 



O. elliptica is a narrow-leaved, inconstant type, exceedingly 

 " difficult of cultivation." Though fertile to its own pollen, it 

 " repeats its type only in a very small proportion of its seeds." 



There are thus " a dozen new types springing from an original 

 form in one restricted locality and seen to grow there, or arising 

 in the garden from seeds collected from the original locality." 

 Most of these types behave with a constancy that ranks them, 

 for breeding purposes at least, as distinct forms, good elementary 

 species, new things in the earth that may be held constant or 

 that may be slightly modified by the exercise of selection among 

 the fluctuations to which all types both old and new are subject. 

 The experimenter observes : 



It is most striking that the various mutations of the evening primrose 

 display a great degree of regularity. There is no chaos of forms, no indefi- 

 nite varying in all degrees and in all directions. On the contrary, it is at 

 once evident that very simple rules govern the whole phenomena. 



History of the experiment. In all De Vries made four differ- 

 ent series of pedigree cultures of the evening primrose, extend- 

 ing from five to nine generations and including thousands of 



