270 GENETICS 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, Mnothera 
rubricalyx (Fig. 118) has been known to occur but once in all CEnothera 
cultures and then in a single plant. The red sunflower, 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 
ae vegetative mutations, as distinguished from 
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 
Tia, dite eua) oor Oe of the undifferentiated cells of the very 
from a white flowered young shoot. Just as in the case of factor 
gladiolus bearing red flow- mutations in germ cells, so in vegetative muta- 
ers ononesideof thestalk =, 5 - ae 
and showing one flower tions the somatic effects range from single visible 
half red and half white; ¢haracter differences to manifold effects in which 
asectorial chimera (see i i 
Chapter XXII). 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 “‘The Bride” is a white variety of Gladiolus colvillet, 
a red-flowered form, and doubtless originated from it as a seed or bud 
mutation. In 1915 there appeared in a row of “The Bride” a single 
stalk bearing partly red and partly white flowers. That this grew from 
a corm which was an offshoot from a typical white-flowering corm is 
certain. Furthermore, that the mutation occurred very early in the 
development of this corm and not sometime during the growth of the 
flower stalk is proved by the following observation. In the autumn 
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