42 GENETICS [Bot. Absts., Vol. V, 



326. Becker, J. Beitrage zur Ziichtung der Kohlgewachse. [Contribution to the breed- 

 ing of the Brassicas.] Zeitschr. Pflanzenziicht. 7: 91-99. Dec, 1919. 



327. Bergh, Ebbe. Studier over ddvstumheten i Malmohus Ian. [Studies on deaf- 

 dumbness in the district of Malmohus, Sweden.] 185 X 250 mm., 199 p. Stockholm, 1919. — 

 Among deaf-and-dumbs there are a greater number of individuals with brown or black hair 

 and brown eyes than among normal persons in Sweden. The author considers that this fact 

 is caused by descent from immigrant darker types. He points out that there is scarcely any 

 chance to restrain the consanguineal deaf-dumbness by legal directions. — K. V. Ossian 

 Dahlgren. 



328. Biggar, H. H. The relation of certain ear characters to yield in corn. Jour. Amer. 

 Soc. Agron. 1 1 : 230-234. 1919. — Relationship of four ear characters to yield has been measured 

 for five varieties of maize. The ear characters chosen were weight, length, numbers of rows 

 and shelling percentage. Data were obtained for a period of several years. It was found 

 that ear length was the most consistent index of subsequent yield though the highest correla- 

 tion coefficient found in the series was between weight and yield. The author concludes that 

 these four ear characters are not closely enough associated with yield to be of value as a basis 

 for selection. — J. H. Kempton. 



329. Bixby, W. G. The butternut and the Japan walnut. Amer. Nut Jour. 10: 76-79. 

 82, 83, 11 fig. 1919. — Occurrence of rough-shelled walnuts on American-grown trees of the 

 two Japanese species, Juglans cordiformis and J. Sieboldiana, is discussed, illustrated and 

 convincingly explained as due to natural hybridization between the above species and the 

 closely related native American species J. cinerea. Reference is also made to the possibility 

 of producing new superior hybrid varieties between these oriental and American species which 

 can be grown throughout a greater range of latitude than these walnuts at present occupy. 

 — E. B. Babcock. 



330. Blakeslee, Albert F. Sexuality in mucors. Science 51 : 375-382, 403-409. 4 fid- 

 April 16 and 23, 1920.— Mucors are divided into two groups as regards sexual reproduction: 

 (1) homothallic or hermaphroditic forms, and (2) heterothallic or dioecious forms. The 

 latter are by far the most abundant in nature. — Sexes of different dioecious species show an 

 imperfect sexual reaction and produce gametes which, however, never fuse. By this "imper- 

 fect hybridization" reaction the sex of unmated dioecious races may be determined. In 

 dioecious species there are two types of zygospore germination. In one case the spores in a 

 germsporangium are all of same sex, but in the other the spores are of both sexes. Environ- 

 mental factors have a direct influence on zygospore formation. Many "neutral" races have 

 been found which give no sexual reaction inter se or with testers of other species. The appar- 

 ent neutrality of such races may be due to lack of the peculiar environmental conditions neces- 

 sary for expression of the sex which is actually present. All dioecious species investigated 

 are sexually dimorphic. Author discusses gamete differentiation in mucors and its possible 

 significance in relation to sex differentiation in higher forms. — W. H. Eyster. 



331. Bliss, A. J. Hybrid bearded Irises. Gard. Chron. 67: 76, 88. Feb. 14, 21, 1920 — 

 Older varieties of June-flowering bearded Irises may be referred to two main species, pallida 

 and variegata, or combinations of the two. Amoena is a color variety of variegata, due to in- 

 hibiting factor for yellow or absence of factors for yellow present in variegata. Neglecla is 

 squalens minus yellow. Several hundred crossings of plicata color type do not yield conclu- 

 sive evidence of origin. Characteristic beard is carried through generations of transition 

 seedlings in which it has disappeared along with plicata color characters, reappearing unaltered 

 in succeeding individuals of plicata color type. Plicata crossed with pallida or squalens- 

 pallida forms give plicata only. Crossed with pallida or variegata the plicata type disappears 

 but when crossed with certain neglectas or sguaZens-carrying plicata the Mendelian ratio of 

 one-half plicatas is obtained, suggesting that the plicata type has arisen as a mutation from 



