Apeil 3, 1914] 



SCIENCE 



489 



been unfortunately introduced even into ele- 

 mentary courses of botanical or biological in- 

 struction. Europe has presented a marked 

 contrast to America in this respect, for here 

 the mutation hypothesis of De Vries has been 

 coldly received. It seems clear however that 

 the European attitude is more in accordance 

 with the established principles of biology than 

 our own. 



The distinguished English geneticist Bate- 

 son was apparently among the first to point 

 out that in all probability (Enothera lamarch- 

 iana was a hybrid, as shown by the partial 

 sterility of its pollen. Dr. MacDougal coun- 

 tered by the statement that he had found 

 abortive pollen in specimens of 0. hiennis, 

 growing in the vicinity of the city of New 

 York. This he apparently regarded as a suiS- 

 cient reply to Professor Bateson's criticisms. 

 More recently a number of American students 

 of plant genetics have cast doubt on the gene- 

 tieal purity of De Vries's (Enothera lamarck- 

 iana. Among these may be mentioned Davis, 

 East, Emerson and Gates. The attitude of the 

 last investigator is not the less significant be- 

 cause he was in the first instance a convinced 

 mutationist of the De Vriesian school. In 

 the case of the mutation hypothesis, we find 

 again what is apparently an all too common 

 condition in the case of biological theories, a 

 neglect of fundamentally important morpho- 

 logical evidence. There seems to be absolutely 

 no doubt, on morphological grounds, that not 

 only is CEnothera lamarchiana of hybrid 

 origin; but that the Onagraceas, to which it 

 belongs, are somewhat generally contaminated 

 by spontaneous hybridism. 



I have delayed publication of my conclu- 

 sions in regard to the genetical status of the 

 Onagracese, in the hope that some other mor- 

 phologist would lay bare the extremely inse- 

 cure foundations upon which the imposing 

 superstructure of the mutation hypothesis has 

 been raised. About eight years ago cultures of 

 0. lamarchiana and its mutants were started 

 at the Harvard Botanic Garden from seeds 

 supplied by Professor De Vries. (Enothera 

 grandiflora, which was of special interest in 

 connection with the mutation hypothesis, was 



likewise grown from seed supplied by Pro- 

 fessor S. M. Tracey who made a special visit 

 to Tensaw to obtain it for me. Shortly after- 

 wards other work became more pressing and 

 monopolized all available time. The cultures 

 and seeds were accordingly turned over to 

 Professor Bradley M. Davis, who was residing 

 in Cambridge at that time. Dr. Davis has 

 published a number of papers on hybridization 

 work with (Enothera species and I have sup- 

 plemented my original stock of preserved 

 material from specimens kindly supplied by 

 him. 



Some illustration of pollen conditions in 

 known hybrids other than Onagracese wiU first 

 be considered. Many of our improved horti- 

 cultural plants are known to have originated 

 by hybridization, while others more anciently 

 cultivated by our species are suspected of hy- 

 brid origin. Taking only the known hybrids 

 as illustrations, such as tulips, irises, narcissus, 

 lachenalia, freesia, etc., etc., we find that al- 

 though many of the pollen grains are per- 

 fectly developed both as regards external 

 form and internal contents, a greater or 

 smaller proportion are small, shrivelled and 

 nearly or quite devoid of protoplasm. In the 

 case of genetically pure species of these genera 

 the pollen grains on the contrary are all alike 

 and perfect. In normal species, even when 

 long in culture and under hothouse conditions 

 the pollen has proved in all the cases examined 

 in the present connection perfectly sound. 

 This is notably the case for example with the 

 common easter lily. The effect of hybridiza- 

 tion is equally clear in the case of the Dicoty- 

 ledons. Our pinks, calceolarias, nasturtiums, 

 etc., are often of known hybrid origin and 

 show clear evidence of such derivation in the 

 condition of their pollen, which is more or 

 less abortive. President Brainerd, of Middle- 

 bury College, has in recent years made some 

 interesting observations on spontaneous hy- 

 brids of our native violets. He has found 

 numerous forms of these, significantly de- 

 scribed by certain systematists as new species, 

 to be in reality hybrids, as shown by their 

 characters clearly intermediate between recog- 

 nized species and by their Mendelian segre- 



