A LECTUEE ON THE HEEEDITARY CHARACTERS IN THE POTATO. 35 



the upper. In S. verrucosum there seems reason to beHeve that both 

 surfaces are free from inhibitors. There may thus be said to be five 

 pairs of factors deahng with fiower colour. There is probably no 

 relation whatever between any of these flower characters and the 

 quality or shape of the tuber. 



Sterility of the Anthers —I have already pubhshed- some of the 

 earlier evidence I obtained on this subject, and I am not prepared to 

 say more than that the dominance of sterility is an undoubted fact, 

 but it is probably not such a simple matter as I first thought and repre- 

 sented. To practical breeders the fact of dominant male sterility is 

 one of some slight value. I do not find that male sterility is correlated 

 with great cropping power or any other economic character, as has 

 been frequently suggested. 



Shape of the Berry. — The berries of the domestic varieties are 

 round, whilst of wild types, such as S. etuderosum, S. verrucosum, 

 S. tuberosum, and S. Commersonii, they are long. Consideration of 

 the seedlings of aS'. etuherosum, together with all their crosses, showed 

 clearly that the length of the berry was due to a single pair of factors, 

 that when pure to length the berry was either very long and pointed 

 or very long and blunt. When the individual was hybrid as regards 

 length, the berry was heart shaped; when pure to shortness it was 

 round ; and such round-berried plants breed true as regards the shape of 

 the fruit. 



The Haulm.. — Only one conclusive result has emerged from my 

 observations on the haulm, and before adverting to that I will 

 just say that the colour of the stem is doubtless controlled by factors 

 similar to those of the tuber. Segregation of coloured versus green 

 stems is often most pronounced, but there are many and real difficulties 

 in making sufficiently accurate distinctions between one typo of stem 

 colour or foliage and another to allow of numerical treatment. 



The one hereditary character, however, which is clearly controlled 

 by a single pair of factors is that of the upright and prone habit. 

 Potato-growers have put on the market innumerable seedlings, and all 

 of them, as far as I know, grow upright, at any rate during the major 

 part of the season. When, however, the potatos begin to die down, 

 or, as a result of disease, the haulms decay, then a noticeable differ- 

 ence may be observed between one variety and another. Some, even 

 when dead, whether from natural causes or through disease, stand 

 bolt upright. Such potatos, for example, are ' Up-to-date ' and ' Table 

 Talk.' Others, when nearing the fulness of their growth, tend to 

 become bushy, and the lower branches, if not the entire haulm, come 

 gradually to lie on the ground. In my experiments I have found 

 that there is still a third class of seedlings, and that is one in which 

 from birth onwards the plants lie flat on the ground. These have 

 not the power to grow erect. 



The " bushy " plant (i.e. the one that droops towards the' end of 

 its growth), such as ' Flourball ' and ' Early Eegent,' is heterozygous 

 * Jour. Linn. Soc. Bot. xxxix. (1910), p. 301. 



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