. Genetics in relation to agriculture. Livestock; Heredity; Variation (Biology); Plant breeding. 270 GEN Erics IN RELATION TO AGRICULTURE seedlings indicate that, as in animals, germinal mutations usually occur just before or during the maturation process. The strongest evidence for this conclusion is the fact that, so far as known, new dominant char- acters appear first in only one or two individuals. The following cases illustrate this point. The red-leaved evening primrose, CEnothera ruhricalyx (Fig. 118) has been known to occur but once in all ffinothera cultures and then in a single plant
. Genetics in relation to agriculture. Livestock; Heredity; Variation (Biology); Plant breeding. 270 GEN Erics IN RELATION TO AGRICULTURE seedlings indicate that, as in animals, germinal mutations usually occur just before or during the maturation process. The strongest evidence for this conclusion is the fact that, so far as known, new dominant char- acters appear first in only one or two individuals. The following cases illustrate this point. The red-leaved evening primrose, CEnothera ruhricalyx (Fig. 118) has been known to occur but once in all ffinothera cultures and then in a single plant. The red sunfiower, Helianthus lenticularis coronatus, as reported by Cockerell, first appeared as a single plant which proved later to be a heterozygous dominant. A purple-leaved mutation in hemp. Cannabis sativa, is reported by Dewey to have first appeared in two pistillate plants in a closely inbred strain of normal green plants. Had these mutations occurred at some preliminary stage in germ-cell formation, the change in chemical constitution would have been transmitted to several or many gametes and a considerable number of individuals would have appeared instead of only one or two. Factor mutations in meristematic cells, or vegetative mutations, as distinguished from r those originating in the germ cells, give rise to simple bud. sports or to chimeras according to the location of the mutating cell. A bud sport is a shoot or branch which differs genotypically in one or more characters from the remainder of the plant. Here the factor mutation must occur in one of the undifferentiated cells of the very young shoot. Just as in the case of factor mutations in germ cells, so in vegetative muta- tions the somatic effects range from single visible character differences to manifold effects in which many structural details are different. An example of bud sports in which the factor mutation induced a single character difference is shown in Fig. 111. The early gladiolus known as &qu
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