758 THE AMERICAN NATURALIST. [Vol. XXXVII. 



knowledge is concerned, has no exact duplicate in the native 

 flora of any region, and two probabilities are suggested as to its 

 origin : It may have been a native of a restricted range in " Vir- 

 ginia" in which it has been exterminated by agricultural opera- 

 tions, and hence cannot be found at the present time : or it may 

 have arisen by some such sudden, and abrupt, discontinous vari- 

 ation, as that by which deVries' mutants came into existence, 

 from 65". biennis in the gardens, at Padua, Altdorf or else- 

 where : at least no intermediate forms are known." 



Only eleven specimens of hybrid seedlings derived from 

 CEnothera lata were brought to the adult stage, in my cultures 

 and of these but two conformed to the type of Qi. lata, the 

 remainder being the O. lamarckiana form. CE. lata does not 

 perfect its stamens but it is capable of being pollinated from the 

 parent. The offspring followed the laws governing parent and 

 mutant hybrids, which with deVries were found to consist of 

 i8% to 20% of the mutant type and the remainder of the par- 

 ent. My own results agree with this. It is clear that this form 

 would not have survived beyond the season of its appearance as 

 it does not display any marked propagative capacity. 



QinotJiera nanella originated in deVries' s cultures in 1888 

 and has since been followed by him through fifteen seasons. 

 The qualities of this form separate it from the parent in such 

 manner that it might be considered as a variety by some sys- 

 tematists, although its behavior and physiological properties are 

 constant and very clearly distinguishable. In following out 

 the development of the plant during the eighteen months over 

 which my own observations extended it became evident that it 

 differs most widely from the parent in its earlier, and also in its 

 adult stages, being most like it in the full rosette stage. The 

 most apparent feature is its diminutive size, both in the young 

 plant and in the mature flowering shoot. The stem shows but 

 little capacity for branching and did not reach a height of more 

 than 20 to 25 cm. in my cultures, or about one fourth that of the 

 parent, which sends out numerous vigorous branches. The first 

 few leaves have very broad laminae with irregular apical portions, 

 and are short petioled. Later leaves are more nearly like the 

 parent type but remain shorter petioled which has the effect of 



