314 



GENETICS IN RELATION TO AGRICULTURE 



smaller forms. That is, a dwarf form may spring from a large form or 

 from another dwarf form as shown in Fig. 130. Another distinct group 



FIG. 130. Bud mutations in sports of the Boston fern. At the right (6) is the form, 

 magnified, a dwarf, asexual descendant of the variety, bostoniensis. The fern in the center 

 (a) is a sport from this dwarf. It has a tendency to produce further sports and so could not 

 be depended upon to breed true. At c is shown a small plant whose single frond resembles 

 magnified. At d is another sport that already displays instability in having two sorts of 

 fronds. (After Boshnakian.) 



FIG. 131. A series of pinna* illustrating progressive variation in division. 1, Var. bos- 

 toniensis; 2, Piersoni; 3, Whitmani; 4, Goodi (or gradUima); 5, Magnified; 6, Craigi; 

 7, Amerpohli. (Courtesy Brooklyn Botanic Garden.) 



(Courtesy Brooklyn Botanic Garden.) 



contains the more delicate, open, lace-like forms, such as Millsii and 

 verona (Fig. 1296, d). The latter has an advantage over several earlier 



