104 PROBLEMS OF GENETICS 



1 do not mean to suggest that these Oenotheras follow a simple 

 Mendelian system. All that we know of them goes to show that 

 there are curious complications involved. One of these, prob- 

 ably the most important of all, has lately been recognized by 

 de Vries himself, namely, that in certain types the characters 

 borne by the female and the male germ-cells of the same plant 

 are demonstrably different. There can be little doubt that 

 further research will reveal cognate phenomena in many unsus- 

 pected places. The first example in which such a state of things 

 was proved to exist is that of the Stocks investigated by Miss 

 Saunders. 2 By a long course of analysis she succeeded in estab- 

 lishing in 1908 the fact that if a plant of Matthiola is of that 

 eversporting kind which gives a large proportion of double- 

 flowered plants among its offspring (produced by self-fertili- 

 sation), then the egg-cells of such a plant are mixed in type, but 

 the pollen of the same plant is homogeneous. Some of the egg- 

 cells have in them the two factors for singleness, but some of 

 them are short of one or both of these factors. The pollen- 

 grains, however, are all recessives, containing neither of these 

 factors. The egg-cells, in other words, are mixed, "singles" and 

 "doubles," while the pollen-grains are all "doubles." The same 

 is true of the factor differentiating "white," or colourless plastids 

 from cream-coloured plastids in Matthiola, the egg-cells being 

 mixed "whites" and "creams," while the pollen-grains are all 

 "creams," viz: recessives. Later in the same year (1908) 

 de Vries 3 announced a remarkable case which will be discussed 

 in detail subsequently. It relates to certain Oenotheras hetero- 

 zygous for dwarf ness, in which (p. 113) the ovules were mixed, 

 tails and dwarfs, while the pollen is all dwarf. 



Again in Petunia Miss Saunders's 4 work has shown that 

 a somewhat similar state of things exists, but with this remark- 

 able difference, that though the egg-cells are mixed, singles and 

 doubles, the pollen-grains are all singles, viz: dominants. All 

 the Petunias yet examined have been in this condition, including 



2 Rep. Evol. Ctee. R. S., IV, 1908, p. 38. 



3 Ber. Deut. Bot. Ges., 1908, XXVI, a, p. 672. 



4 Jour. Genetics, i, 1910, p. 57. 



