362 i, diy. ANID IDNR 
steak at = Gr 
The constitution of the green pea is G) 
|G| 
kind only, namely G. If we unite equal numbers of Y and G with G only, 
, and it produces gametes of one 
we get equal numbers of and e) that is equal numbers of the 
ng 
G 
yellow hybrid and of the pure green. This result is again in accordance 
with experiment. 
So far we have considered in each case only one pair of alternative 
characters. There are of course often a number of such pairs existing 
at the same time, each pair of which behaves in accordance with Mendel’s 
law. This gives us a result which perhaps appears at first sight to be 
more complex than it really is. Diagram 5 (p. 364) represents a case 
studied by Mendel in peas, in which two pairs of characters are involved. 
First we have the two colours, yellow and green, which have already 
been considered. At the same time, some of the peas are round in shape, 
whilst others are very much wrinkled, the wrinkling being really dependent 
upon the character of the starch grains which constitute the bulk of the 
pea. In the diagram yellow is represented by a broad black le, green 
by a broad white line, wrinkled by a broken line. 
If we cross-fertilise flowers from a plant bearing pure yellow, wrinkled 
peas with those of one bearing green round ones, we get in the 
first hybrid generation yellow round peas. Yellow is dominant to 
green, as we already know, and round is dominant to wrinkled, which is 
recessive. 
Plants grown from such double hybrid peas were allowed to self- 
fertilise and four kinds of peas were produced: yellow round, yellow 
wrinkled, green round, and green wrinkled. Mendel’s figures for this 
cross are shown below, the figures required by theory being placed under- 
neath them : 
Yellow Yellow Green Green 
round. wrinkled. round. — wrinkled. 
Mendel’s Experiment . 315 10] 108 32 
Theory : : Meson 104 104 35 
9) : 3 3 3 : ] 
The combination which contained two dominants, yellow and round, 
was most numerously represented, that contaiming two recessives, green 
and wrinkled, was least numerous. 
The theoretical analysis of the case is as follows :-— 
Let Y=yellow, @=green, R=round, W=wrinkled. 
