88 REPORT OF THE CONFERENCE ON GENETICS. 
generation from the cross. Of the yellow seeds of this second generation 
it was found that some bred true to yellow, and some not; the former, 
therefore, he called “ pure’’ yellow, and the latter “ hybrid ’’ yellow; and 
he proved the pure yellows through several generations and found them 
to keep true, showing no reappearance of the green recessive ancestry. 
But the others—the hybrid yellows—produced, pure yellow and hybrid 
yellow and pure green, just as their parents had. It should, however, 
be borne in mind that the pure yellow and the hybrid yellow seeds are 
exactly similar to the eye, and only by sowing them and noticing their 
progeny can it be discovered which individual seeds are pure yellow 
and which hybrid yellow; but Mendel discovered by long experiment 
that though they are indistinguishable to the eye, yet the pure and 
the hybrid yellows bear to one another the proportion of one pure to 
two hybrid or impure. So that we get the following law of inheritance :— 
Yellow x Green (or vice versa) 
Ist Generation . : : : all yellow 
| ; 
2nd Generation. : . 3 yellow to . j C : : : . I green 
| 
3rd Generation 1lpure to 2 impure to : , ; : l green green 
yellow yellow 
ve 
| oa | 
4th Generation pure i pure to 2 impure to 1 green’ green green 
yellow yellow yellow | | 
| sone 
| | | 
5th Generation pure pure limpure 2 pure 1 green green green _ green 
yellow yellow’ yellow yellow 
and so on in a continuing series, the impure or hybrid yellow seeds, as 
they are called, producing with fair constancy a proportion of one seed in 
every four which will prove (on being sown) to be a pure yellow and one 
which will be seen to be green, the two remaining seeds being impure 
yellow, which will in turn repeat the same result as their immediate 
parent. 
In other words, if you cross pure yellow and pure green peas either 
way—it matters not which is seed-bearer and which pollen-bearer—you 
will get all yellow seeds. If you sow these hybrid seeds, each will, if it 
germinates, produce a plant which will bear, say, forty seeds, thirty of which 
will on the average be yellow, and ten green. The green, if sown and sown 
and sown for countless generations, will always bear green seeds, true to 
the original green parents (barring the always possible intervention of 
insects). Not so the thirty yellow. These when sown will on the average 
produce ten plants bearing all pure yellow seeds, which will be constant 
and true to the original yellow parent for countless generations. The 
remaining twenty plants will be impure yellows, each plant producing on the » 
average one quarter of their seeds pure yellow, one quarter pure green, and 
one half impure yellow, which last will repeat the process and proportion 
practically for ever. 
