214 POPULAR SCIENCE MONTHLY. 



quantity among 50,000 other plants. To this it may be replied that 

 the phenomenon of fluctuating variation, as it appears in Oenothera, 

 has been studied in detail by de Vries and has been exactly determined 

 both for the central species and for the different subspecies (mutations). 

 In all of them it occurs on a large scale, but not one of the speci- 

 mens above mentioned belongs to it. These 800 have very special 

 characteristics, by which they can be sharply distinguished from the 

 fluctuating variations. And, as is especially remarkable, they are not 

 in every respect different from each other, but may be arranged in 

 seven natural groups, each of which possesses exactly the same sys- 

 tematic value as that particular combination of specific characteristics 

 to which the name of Oenothera Lamarclciana has been applied. 



The number of individuals of those seven groups, of which de Vries 

 has observed the spontaneous appearance, is, however, most unequal 

 and varies between 1 (CEnothera gigas), 56 (Oenothera albida), 350 

 {Oenothera oblonga), 32 {CEnothera rubrinervis) , 150 (CEnothera nan- 

 ella), 221 (CEnothera lata) and 8 (Oenothera scintillans). 



De Vries has studied the mutations thus arising, some of which are 

 rare and some more common, with the utmost care, and has followed 

 them during the whole of their existence. 



Oenothera gigas, which has only once arisen in the Lamarckiana 

 group and which is characterized by much larger-sized flowers, a dif- 

 ferent shape of the leaves that form a rosette at the root, more thickly 

 set leaves along the stem, etc., was sown by de Vries in 1897, after he 

 had obtained seed, thanks to artificial fecundation, the possibility of 

 self-fertilization being excluded. He thus obtained 450 plants, which, 

 with the exception of a single one, exhibit all the characteristics of the 

 CEnothera gigas with perfect constancy. The exception was not a 

 retrogression towards O. Lamarckiana, but a new deviation, provision- 

 ally indicated as O. gigas nanella. From 1898 to 1900 further propa- 

 gation by seed has been effected during three generations and under 

 very strict precautions; and until now all the descendants of that one 

 mutation of 1895 remain perfectly constant; de Vries has actually 

 seen the species O. gigas come forth out of O. Lamarckiana, first in 

 nature, afterwards in his own nursery-garden. It appears to be a very 

 strong plant, which, if it had to fight for its existence against O. 

 Lamarckiana, in equal numbers and under the same circumstances, 

 would probably prove to be the winner. 



The second mutation, Oenothera albida, which occurred 56 times 

 during the experiments, shows another character. It is a feeble plant, 

 and was originally considered a pathological deviation, which, however, 

 in the later generations has proved itself to be none the less constant, 

 and, though but little fertile, produced 86 plants in 1898 and 36 in 

 1899. 



