386 GENETICS IN RELATION TO AGRICULTURE 
pagated. Careful inspection may reveal a certain number of chimeras 
and bud sports. Both, in fact, are comparatively common in some 
varieties, such as the Boston Fern and the Washington Navel Orange, 
and they sometimes give rise to superior new biotypes. Yet inspection 
alone is not sufficient. A new fern sport must be propagated in order to 
test its constancy when multiplied vegetatively. Similarly a supposed 
orange sport must be propagated and the progeny must be tested in’ 
order to ascertain whether the selected phytomer is really a mutation 
and a desirable one at that. 
Having discovered a new type which originated by bud mutation, 
the question arises: Will there be any practical difficulty in maintaining 
this new form by means of vegetative propagation? Are additional 
somatic mutations likely to occur in sufficient number to endanger the 
preservation of the selected form? It will be remembered that sometimes 
bud mutations in the Boston Fern produce ever-sporting varieties that 
have little or no commercial value. Similar inconstant forms have 
arisen in other ornamentals. Nevertheless it has been practicable 
to propagate vegetatively many valuable bud sports and hybrids, in- 
cluding some that are highly variable. One such product of composite 
hybridization is the cultivated Coleus. This ornamental foliage plant 
is commonly used for beds and borders in summer and as a conserva- 
tory plant in the colder months. The foundation stock was produced 
in England about 1867 by hybridizing four different exotic species. 
Hundreds of named varieties have been produced, some having appeared 
as bud mutations, but the majority being seedlings. Some of the varie- 
ties now in cultivation are characteristically variable. In one such 
variety Stout has investigated the variations in leaf color pattern and 
leaf shape in a series of 833 plants, all descended by vegetative 
propagation from two similar plants. 
Bud Selection in Coleus.—The two plants with which Stout began 
had a definite pattern of leaf coloration consisting of a green mid-region 
and yellow border with blotches of red in the epidermis (Fig. 159). The 
green and yellow pigments exist in the sub-epidermal layers. The 
vegetative offspring from the two original plants were kept separate and 
the simple habit of branching in this plant made it possible to indicate 
the particular branch as well as the individual plant from which a cutting 
was taken. In this way Stout was able to trace the pedigree of any plant 
to its original source. During the course of the investigation 16 new 
color patterns were obtained. There also appeared the laciniate form 
of leaf which is seen in the younger leaves of the plant on the left in Fig. 
159. Of the 16 new color patterns 15 arose by somatic mutations which 
produced bud sports either directly or, in some cases, indirectly from 
chimeras. The other new pattern arose solely as a fluctuating variation, 
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