236 Mendel's Laws of Alternative Inheritance in Peas 
II. — Other Evidence concerning Dominance in Peas. 
It is certain that an alternative inheritance, which may produce something 
like Mendel's phenomenon of segregation, occurs as a result of crossing races of 
animals and plants, when nothing comparable with dominance can be observed in 
the immediate offspring of the cross. The two phenomena must therefore be 
considered separately (cf Correns, No. 5). 
The evidence concerning dominance in the first hybrid generation of Peas 
relates chiefly to the colour of cotyledons and seed-coat, and to the shape of the 
hybrid seed. In judging it, we must be careful to realise what the statement, 
that a character is dominant, really means. Many races of Peas are exceedingly 
variable, both in colour and in shape. A race with "round smooth" seeds, for 
example, does not produce seeds which are exactly alike ; on the contrary, 
many seeds of such a race as Victoria, used by Rimpau (No. 26) as a typically 
round and smooth-seeded Pea, or Expi^ess used by Tschermak (No. 27) in the 
same way, show very considerable irregularities ; while in races such as Prince 
of Wales or Telephone, used by Tschermak and others as types of races with 
wrinkled seeds, hardly any two seeds are alike. So that both the category 
"round and smooth" and the category "wrinkled and irregular" include a con- 
siderable range of varieties. At the same time, the categories are undoubtedly 
often discontinuous, the most wrinkled seed of such a race as Express or Victoria 
being so much smoother and more rounded than the most regular seed of the 
typically " wrinkled " races, that no one who knows both races would hesitate for a 
moment in deciding which race a given seed resembled. 
The statement that smoothness of seed is dominant over the production of 
wrinkles means therefore that if a parent, belonging to a variable race which falls 
into the category " smooth -seeded," be crossed with a parent belonging to a 
variable race of the category " with wrinkled seeds," the offspring will themselves 
be variable, but will always belong to the category ''■ smooth-seeded " : and as it is 
with shape, so it is with colour. 
The first detailed account of the colour in hybrid Peas, which I have been able 
to find, is that of Goss, 1848 (No. 15), who fertilised the flower of a "blue-seeded" 
race with pollen of a race with yellowish white seeds. The hybrid seeds were 
all yellowish white; and the plants raised from them "produced some pods 
with all blue, some with all white, and many with blue and white seeds in 
the same pod " ; or the result was probably that obtained by Mendel. In a 
note to this paper, the then Secretary of the Horticultural Society says that 
Mr Alexander Seton crossed the flowers of Dioarf Imperial " a well-known green 
variety of the Pea," with the pollen of " a white free-growing variety." Four 
hybrid seeds were obtained, " which did not differ in appearance from the others 
of the female parent." These seeds therefore did not obey the law of dominance, 
or if the statement be preferred, greenness became dominant in this case. The 
seeds were sown, and produced plants bearing " green " and " white " seeds side by 
