58 MUTATIONS, VARIATIONS, AND RELATIONSHIPS OF THE OENOTHERAS. 



A similar aberrant of 0. cniciata has been found in many of the cultures of 

 that species. Much attention has been devoted to these forms, both as to 

 habits of growth and anatomy. The only parallel occurrences are those 

 which are to be found in other genera in which atypical individuals affected by 

 the enzymatic diseases may give a progeny in which the normal form of indi- 

 viduals predominates. The vigorous growth of the atypic individuals and 

 the comparative regularity with which it appears are well worthy of remark. 

 If these forms were found growing in the open, they might easily be taken as 

 belonging to a species apart from 0. biennis unless their progeny was tested 

 in pure cultures. 



The pedigreed cultures of 0. grandiflora made in 1906 from purely fertilized 

 seeds of the previous year included about 1 500 plants. More than one season 

 of such cultures is necessary to secure definite results that may be depended 

 upon. The observations have been carried so far at the New York Botan- 

 ical Garden and the Desert Laboratory, however, as to warrant the assertion 

 that this species presents a complex progeny analogous to that of lamarckiana, 

 in which two well-defined mutants are readily recognizable by reason of their 

 striking diflferences from the parental form. 



ORIGIN OF FIXED FORMS BY HYBRIDIZATION. 



That the cross-fertilization of two forms may result in the production of a 

 unitypic or polytypic progeny in which the parental qualities appear in a 

 mosaic is well known. Components of a native flora have been suspected to 

 be of hybrid origin in a few instances, and by succeeding experimental tests 

 have been synthetized from the parents. The practice prevailing among 

 taxonomists of ascribing a hybrid origin to a newly discovered form, which, 

 in outward anatomical characters, is between two know^n species, is extremely 

 pernicious and is not justified by facts obtained in cultural work. The best 

 grounds for such a conclusion are to be found when two species alone occur 

 in a region, and the appearance of a third is attributed to hybridization ; but 

 even here the supposition that a mutation may have ensued is allowable. 



The hybrid 0. lamarckiana X 0. cruciata (form with long hypanthium and 

 slender bud), which was described in the previous publication by the authors, 

 proves to be a fixed form, and as it sets seeds freely and is self-fertilizing, it is 

 in every respect an independent species. Several hundreds of seedlings were 

 grown from purely fertilized capsules ripened in 1904, with the result that all 

 w^ere seen to conform to the parental hybrid type in every particular. The 

 two parental forms do not meet in their native habitats, and hence this form 

 could not have arisen in a state of nature. 



The reciprocal of this cross, that is, 0. cruciata X 0. lamarckiana, consists of 

 three forms, one of which is indistinguishable from the 0. biennis cruciata 

 which has been received from various European gardens. 



