Page:Popular Science Monthly Volume 77.djvu/355

Rh by use of the Mendelian theory. For example, two or more hereditary factors may be necessary for the production of an actual tangible character. If factors A and B must be present for its production, then a plant carrying only factor A and another carrying only

 a and b, the two parents, starchy and sweet maize; c, the first hybrid generation showing dominance of starchiness; d, the second hybrid generation showing segregation with the ratio of three starchy to one wrinkled seed. Lower row daughters of d. e, f and g, results of planting starchy seeds. One ear out of three is pure starchy, h, result of planting sweet seeds. Ear is pure sweet.

factor B do not possess the character. But let the two plants be crossed and the character appears. There are two white varieties of sweet peas; each, however, contains one of the two factors necessary for the production