1 82 Ikeno. — On Hybridization of some Species of Salix . II. 
Punnett 1 have obtained, (a) from the heterozygote DR with usual domi- 
nance x recessive, 114 extra toes and 95 normal, i. e. 54-5 per cent, and 45*5 
per cent, respectively, and (b) from the heterozygote DR where dominance 
fails x recessive, 128 extra toes and 15 1 normal, i. e. 457 per cent, and 54*1 
per cent, respectively ; consequently the class (a) contains comparatively 
a little more extra-toed progeny than the class {b). So that there may be 
a very slight inheritance of degree of potency, but this is quite insignificant. 
Much more marked inheritance has been found by Davenport 2 in respect to 
the crosses of Houdan fowls : he has calculated the correlation between total 
number of toes in the two parents and average number of toes in their 
progeny, and found the coefficient of correlation to be equal to +0-683 
+ 0*092. 
Turning to our case, the simple inspection of the results of Expts. 1, 3, 5, 
6 shown in Tables III, IV, V, will immediately indicate to us that the inheri- 
tance of the degree of potency is very significant in the present case. The 
results of our four experiments just enumerated were employed to make the 
following table of correlation : 
Table VI. 
A r ature of Crosses. 
G-type. 
Progeny. 
M-type. 
Totals. 
G-type x G-type and G-type x gracilistyla 1 
(Expts. 1 and 6) 
87 + 184 
32+8 
411 
M-type x M-type and M-type x multinervis 
(Expts. 3 and 5) 
4+14 
19 + 91 
128 
Totals 
389 
150 
539 
This gives r = +0*724 + 0-021. The coefficient or correlation is rather 
high, and this result confirms our supposition founded on mere inspection 
of data. 
Since the appearance of the well-known work of Wichura 3 it seems 
that botanists have generally believed in the constancy of Salix hybrids 
throughout later generations. In a short note Sirks 4 has expressed his 
opinion that the work of Wichura by no means induces us to the belief 
that Salix hybrids are constant. In 1916 5 and 1918 6 I published the 
results of my investigations on the hybridization of some species of Salix , 
especially S. gracilistyla and multinervis : in these experiments I was able, 
contrary to the current belief of botanists, to observe the segregation 
of some few characters in Salix hybrids, but since the relative number 
1 Reports to the Evolution Committee of the Royal Society. Report II, 1905, p. 1 1 5. 
2 1. c., p. 23. 
3 Die Bastardbefruchtung im Pflanzenreich erlautert an den Bastarden der Weiden. Breslau, 
1865. 
4 Zeits. f. indukt. Abstamm.- u. Vererbungslehre, Bd. xv, 1915, pp. 164-5. 
5 Bot. Mag., Tokyo, vol. xxx, 1916, pp. 316-20. 
6 Journ. of Genetics, vol. viii, 1918, pp. 35-58. 
