. Genetics in relation to agriculture. Livestock; Heredity; Variation (Biology); Plant breeding. ON VARIETIES IN PLANTS 315 varieties of this group in that its rachis is strong cnougli to support the fully developed frond. As Benedict has shown the bud mutations occurring in these ferns are more commonly regressive (showing more resemblance to boslonien- sis than to their parent forms), but progressive mutations are found from time to time. These progressive changes take place along three main lines, viz., increase in leaf division (see Fig. 131), increase in ruffling or crisping, and dwarfing
. Genetics in relation to agriculture. Livestock; Heredity; Variation (Biology); Plant breeding. ON VARIETIES IN PLANTS 315 varieties of this group in that its rachis is strong cnougli to support the fully developed frond. As Benedict has shown the bud mutations occurring in these ferns are more commonly regressive (showing more resemblance to boslonien- sis than to their parent forms), but progressive mutations are found from time to time. These progressive changes take place along three main lines, viz., increase in leaf division (see Fig. 131), increase in ruffling or crisping, and dwarfing (see Fig. 132); and any form which has not. Fig. ,—A series of fronds illustrating progressive variation in ruffling and dwarfing. 1, A'", exallata; 2, var. hostoniensis; 3, Harrisi (or Roosevriti); 4, Wm. K. Harris (or new sport of Roosevelti); 5, Teddy Jr.; 6-8, dwarf sports of Teddy Jr.; 7, Randolphi. (Courtesy Brooklyn Botanic Garden.) reached the Umits of possibihty in variation along the first and last mentioned Hues, may be expected to give rise to new forms showing further progressive variation in one or both of them. That these new varieties are produced by mutations in specific factors is indicated by the independence of character changes in series of suc- produced forms that differ in several characters; for example, the appearance of dwarf uni-pinnate forms as sports of dwarf multi- pinnate forms. Various series derived from bostoniensis show progressive degrees of reduction in size of frond. When a dwarf tri- or quadri- pinnate plant throws a uni-pinnate sport the latter retains the dwarf size of its parent. Again the difference between Piersom and superbissiina, its sport, consists of the deeper color and twisted, irregular shape of the latter. When it in turn produced viridissima the new uni-pinnate Digitized by Microsoft®. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readab
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