164 



The Journal of Heredity 



brvosacs. In this case the climinati(jii 

 is selccti\'c, and the F-z ratios are akered 

 for fertile and semi-sterile plants, and 

 for cases of linka<,'e. (5) There may be 

 selective jxirtial elimination of pollen 

 ji^rains or embryosacs by sublethal 

 factors (thouj^h this has not yet been 

 proved for any one case). It would 

 of course immediately affect the F> 

 ratios and linkaj^e, if at all extensive. 



Since two or more of these causes of 

 mortality of jjollen grains and embryo- 

 sacs may occur in the same plant, even 

 to determine for instance whether a 

 hybrid plant is precisely semi-sterile or 

 not may require an examination of the 

 pollen from many flowers, and in some 

 cases (as in Citrus species hybrids) for 

 several seasons in succession. 



LITEK.\TURE 



(1) Balls, L. 1909, Rept. of Am. Breed. 

 Assn., 5: 16. Alwrtion of Pollen Greatest in 

 Cokl Weather (in cotton). 



(2) B.M'K, E. 1907, Ber. Deutsch. Bot. Ges., 

 2,S: 442. Lethal Intermediate Factor in Snap- 

 draf^on (chloropliyll factor). 



(3) B.VUR, E. 1914, Einf. in die exp. 

 Vcrerbungslehre, 2 Aufl., BerHn, p. 98. vSub- 

 Ictlial Recessive in Snapdragon (color factor). 



(4) Beach, vS. A. and Manev, T. J. 1912, 

 Rept. of Am. Breed. Assn., 8: 214. Recessive 

 Disease Factor in Prunus Cross. 



(5) Belli.nc,, J. 1914, Zeilsch. f. ind. Abst. 

 u. Vererbitn^slehre, 12:303. Inheritance of 

 Semi-sterility Due to Lethal Combinations (in 

 Stizolobium). 



(6) Belling, J. 1915, Fla. Agr. Exp. Sta. 

 Rei)t. frjr 1914:96. Inheritance of Semi- 

 sterility in Later Generations. 



(7) Bellinc;, J. 1915, Am. Nat., 49:582. 

 Linkage of Late Flowering and Pigmentation of 

 Seed Crjat with One Factor for Semi-sterility. 



(8) BiFFEV, R. H. 1905, Jour. Agr. Set., 

 1 : 4. Selective Elimination Found in Second- 

 Generation Families of Wheat. 



(9j BI1-I.-EN. R. H. 1907, Jouni. Agr. Sci., 

 2: 109. A Sublethal Dominant Disease Factor 

 in Wheat. 



(lOj Cole, R. D. 1917, Bot. Cat., 63: 110. 

 Pollen Abortion in Rosa. 



(11) CoKKENs, C. 1913, Zeitsch. f. iiid. 

 Abst. u. Vererbungslehre, 10: 130. A Recessive 

 Sublethal Factor in Mirabilis. 



(12) Davis, B. M. 1915, Proc. Am. Philos. 

 Soc, 54: 226. Selective Elimination and Stcr- 

 ity in Oenothera. 



(13) DoKSEV, M. J. 1914, Minn. Agr. 

 Exp. Sta. Bull. 144. i'ollen Abortion in Hy- 

 brid and Other Grajjcs. 



(14j East, E. M. 1915, Proc. Am. Philos. 

 ^oc, 53: 70. Pollen Abortion and Fo IClimina- 

 tion in Nicotiana Cross. 



(15) E.mekso.n, R. a. 1912, Nebr. Agr. 

 Exj). Sta. Re[)t., 25:89. Lethal Recessive in 

 Maize ((•hl(>r()i)hyll factor). 



(16) Geekts, J. M. 1909. Rer. des Trav. 

 Bot. Ncerl., 5: 93. Semi-sterility of Oenothera 

 Lamarckiana, and of manv Onagraceae. 



(17) GKECiOKV, E. S. '1907, Journ. of Bot., 

 45: 377. Pollen of Hybrid Violets. 



(18) Gregokv, R. p. 1905, Proc. Camb. 

 Philos. Soc, 13: 148. Polle.i Abortion in 

 Sweet-pea. 



(19) Hoar, C. S. 1916, Bot. Gai.., 62:370. 

 Pollen Abortion in RuVjus. 



(20) Janczewski, E. 1908, Bui. Acad. 

 Sci. Cracovie. Math. Nat., 1908:587. Pollen 

 Abortion in Ribes Hybrids. 



(21) Jekfrev, E. C. 1914, Bot. Gaz., 58: 

 322. AJKjrtion of Microsi)orcs or Pollen grains 

 in Manv Hvbrids and Presumed Hybrids. 



(22) JEFFKEV, E. C. 1915, Am. Nat., 49: 

 1. Pollen of Crvpthybrids. 



(23) jESENKo^ F. 1913, Zeitsch. f. ind. 

 Abst.u. Vererbungslehre, 10: 311. Pollen Abor- 

 tion in Wheat-rye Cross; First Generation Sub- 

 sterile. 



(24) Jones, W. N. Jourti. Genetics, 2:71. 

 Su1)-sterilc Digitalis Sjjecics Cross. 



(25) JuEL, H. O. 1900, Jahrb.f. wiss. Bot.. 

 35 : 638. Pollen Abortion in Presumed Hybrid 

 Syringa. 



(26) Kui'FFER, K. R. 1905, Acta Ilort. 

 Bot. Univ. Imp. Jurjevensis. 6: 1. Pollen 

 Abortion, A Test for .Species Hybrids. 



(27) LiDFORSs, B. 1914, Zeitsch. f. ind. 

 Abst. u. Vererbungslehre, 12: 1. Pollen Abor- 

 tion in Rubus Crosses. 



(28) LiNDSTROM, E. W. 1917, Am. Nat., 

 51:224. Linkage with A Chlorophyll Factor 

 in Maize. 



(29) Miles, F. C. 1915, Journ. Genetics, 

 4: 193. Lethal and Sublethal Chlorophyll 

 Factors in Maize. 



(30) MuECKE, M. 1908, Bot. Zeit., 66: 1. 

 Acorus Calamus, Aborted Pollen and Embryo- 

 sacs. 



(31) Nil.sson-Ehle, H. 1912, Zeitsch. f. 

 Pflanzenzuechlung, 1:3. Sublethal Combina- 

 tions in Wheat. 



in) NiLssoN-EnLE, H. 1913, Zeitsch f. 

 ind. Abst. u. Vererbungslehre, 9: 289. Recessive 

 Lethals in Wlieat and Barley (chlorophyll 

 factors). 



(33) Orton, W. a. 191 U Rapp. 4e. Conf. 

 internal, de Genetique., Paris, p. 247. Sub- 

 lethal (disease) Factors. 



(34) OsAWA, I. 1912, Journ. Coll. Agr. 

 Imp. I nil'., Tokyo, 4:83. Pollen and Em- 

 brvosac Abortion in Citrus. 



(35) OsAWA, I. 1913, Journ. Coll. Agr., 

 Tokyo, 4:237. Abortion of Pollen and lim- 

 bryosacs in Daphne odora. 



'(36) Pellew, C. and Dikham, F. M. 1916, 

 Journ. of Genetics, 5: 159. Abortion of Over 

 Half the Pollen of a Diploid Primula Species 

 Hybrid. 



(37) Renner, O. 1914, Flora, N. F., 7: 

 115. Aborticjn of Zygotes in Oenothera 

 lamarckiana and Its Crosses. 



(38) RosENBERC, O. 1909, K. Sv. Vetcn- 

 kai)s. Akad. Handl., 43, No. II. Abortion of 

 Pfjilen and limbryosacsin aSub-slerile Drosera 

 Hvbrid. 



