Notes. 
1 76 
scion and stock affecting one another \ This, however, is well shown 
in a series of potato grafts 1 2 . The operation was performed by paring 
off a thick piece of skin containing an eye, or a shoot an inch or two 
long, from one potato and binding it tightly over a similarly shaped 
pared patch on another tuber ; all the other eyes were then destroyed, 
leaving only the scion to develop. One set of potatoes {A) had thin, 
smooth-green skins, and numerous deeply sunken eyes, while the 
other (B) was readily distinguished by its thick, rough, brown skin 
and its few shallow eyes. A was grafted on B and B on A, The 
resulting crop of tubers was the same in each case. From one and 
the same plant, tubers of type A and B were obtained (often with 
their characteristics much exaggerated, e. g. the russet skin cracked so 
as to resemble a truffle or the eyes exceedingly deep, &c.), and tubers 
one end of which resembled A, the other B. In many cases there was 
a sharp constriction between the A and B ends, but in some the 
yellowish-green skin gradually passed over into the rough corky skin, 
and the tubers were regular in shape. In every instance the ‘ rose- 
end * (distal end) of the tuber was of the A type, and the heel (proximal 
end) of the B type. Tubers in which the two types were blended 
never occurred. 
Such tubers showing characteristics belonging to both scion and 
stock have long been recognized as typical c graft-hybrids/ and they 
afforded Darwin no small amount of evidence for the theory of 
pangenesis. In describing them as hybrid, however, stress must be 
laid on the facts that if halved transversely each portion is indistinguish- 
able from one of its parents, and that the tuber itself shows all the 
characteristics of its parent and not only certain dominant ones 3 . 
The graft hybrid then is not comparable with the sexually produced 
hybrid in this respect, and in the present state of our knowledge 
it seems impossible to give any adequate explanation of these 
phenomena. 
R. H. BIFFEN. 
Cambridge. 
1 Cf. Lindemuth, Gard. Chron. , 1902, vol. xxxi, p. 61. 
2 For literature see Darwin’s Variation of Animals and Plants under Domestica- 
tion, p. 420. 
3 Cf. Mendel, Joum. Roy. Hort. Soc., 1901, vol. xxvi, p. 1. 
