No. 556] DEVELOPMENT IN NICOTIAN A 207 



tdbacum fasciata. On the other hand, many examples 

 of fasciation are slight or severe somatic modifications, 

 no more permanent than a swollen limb due to a bruise 

 in our own bodies, or a bone spavin in a horse's foot, 

 though the tissue proliferation may remain as a lasting 

 scar. Examples of this form may be found in (Enothera, 7 

 Nasturtium, 8 Picris hieracioides and Raphanus raphan- 

 istrum. Such modifications are imperfectly under- 

 stood, but may be brought about directly or indirectly 

 by external agencies such as bruises, culture methods 

 and insect injuries to the initial meristem. 



Aside from the work of Mendel 10 and De Vries, 11 the 

 phenomena of fasciation have not been dealt with in the 

 light of modern genetics. Mendel's investigations were 

 made on a fasciated strain of pea (Pisum sativum unt- 

 bellatum). When crossed with a non-fasciated strain 

 the teratological character was recessive and segregated 

 in F 2 in a simple 3 :1 ratio. This result was essentially 

 confirmed by Lock and Bateson, although environmental 

 conditions were found by them to affect the character 

 more than is usual in such phenomena. 



De Vries failed to distinguish between fasciations 

 strictly heritable and those non-heritable. The only con- 



Exp. Sta. Bull, No. 167, and Contrib. from Lab. of Genetics, Bussey Inst, 

 of Harvard Univ., No. 9, p. 133, PI. XXII (a) and (b), 1911; also Emerson, 

 R. A., personal communication, 1911. 



7 Knox, A. A., "Induction, Development and Heritability of Fascia- 



^ 8 Knox, A. A., ibid., p. 14. 



Bev. Gen. de Botanique, 12: 323-327, 1900; also Godron, A., "Melanges de 

 teratologie vegStale," Mem. Soc. d. Sc. Nat. d. Cherbourg, 16: Sl-127, 

 pp. 96-97, 1871-1872. 



"Mendel, G. J., "Versuehe uber Pflanzen-Hybriden," Verh. Xaturf. 

 Ver. in Brunn, 10 Abh., p. I. See Bateson, W., "Mendel's Principles of 

 Heredity," pp. 322, 328, 330, Cambridge Univ. Press, 1909. 



"Be Vries H., ibid., Ill, "The Inconstancy of Fasciated Races," pp. 

 488-526, 1910; " Monstruositfe h<§r4ditaires offertes en echange aux Jardins 



Eev. Gfn. de Bot., 2: 136, 1899. 



