822 JOURNAL OF THE ROYAL HORTICULTLIRAL SOCIETY. 



food and water, such plants could be reproduced over practically a j 

 whole field. — M. L. H. 



Potato, Inheritance of Colour and Other Characters in. By 



R. N. Salaman, M.D. {Jour. Gen. i. pt. i. p. 7, Nov. 191U).— This 

 paper forms an important contribution to- our knowledge of heredity 

 in potatos. The author has found that male sterility in the potato is 

 strictly dominant (unlike that in the Sweet Pea, where it is recessive). 

 No case of a plant with pale heliotrope flowers producing fertile anthers | 

 has been discovered. No connexion could be discerned between the ' 

 condition of the male and female organs. 



The characters of leaf shape and texture, while they segregate in j| 

 the generation, appear to be closely linked together. They are, 

 however, difficult of classification, the personal element being so weighty ; 

 in these matters. 



A series of crosses were made (the resulting tubers being ' 

 figured), w^hich appear to show that the long tuber is dominant over the j 

 short ; thus round tubers are probably recessive. The author considers 

 ' kidney ' potatos the most likely to vary as being heterozygous ; if that 

 be so a ' kidney ' potato may give rise to a ' round ' by a ' bud sport,' 

 and if the only factor involved is a length factor, then the round tuber ' 

 ought, at least generally, to breed true to roundness. 



The depth of the eye is another character which is apparently ! 

 inherited on Mendelian lines. Out of 356 plants in the generation 

 arising out of crossings between shallow-eyed and deep-eyed grand- 

 parents, 91 were shallow-eyed, 265 deep-eyed. Apparently, therefore, 

 shallowness of eye is a pure recessive and deepness is dominant, but 

 the heterozygote is somewhat intermediate in this character, though 

 most nearly deep. 



The author finds that in no potato is colour altogether absent from 

 the stem, although in some cases it is difficult to discern. To bring 

 colour out in the tuber, however, a special factor, which he denomi- 

 nates D, must be present; and to produce red a further factor, R, and 

 purple, still another, P; the purple colour not being developed unless 

 all three factors P, E, D are present, as well, of course, as the chromo- 

 gen factor (which, as just stated, appears never to be absent) 0. 



Solanum etuberoswm of Lindsay (see vol. xxxv. pp. 53, 56) was 

 used in some of these crosses. This, for twenty years infertile and 

 immune from attack by Phytophthora infestans, lately bore fruits and 

 was attacked by the fungus. " With the onset of sexual activity some 

 disturbance in the mechanism by which the plant had hitherto secured 

 immunity to Phytophthora had occurred." The author regards 

 S. " etaberosuin " as heterozygous in respect of immunity and finds 

 (in 1909) some innnune plants among the seedlings (7 out of 40). 

 These plants remanied immune, though fully exposed to infection in 

 1910. Resistance to Phytophthora is apparently a recessive character. 



S. " et III) ero sura " is not subject to the same laws of dominance, 

 with regard to shape, eye, and colour of tuber, as the common potato, 

 and is, therefore, probably not to be regarded as a variety of that 



