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THE AMEBIC AN NATUEAIIST [Vol. LI 



grees for all cases, beginning a new pedigree whenever 

 two lines of descent are combined by crossing.^ It is 

 adapted to self-fertile organisms, and its convenience and 

 usefulness obviously increase with the frequency of 

 selfing. Pearl's (1915) "system of recording types of 

 mating, ' ' on the other hand, is especially adapted to dioe- 

 cious and self-sterile organisms, and in general its use- 

 fulness for recording or presenting data increases with 

 the frequency of crossing. 



Several systems similar to Webber's have been described 

 in recent genetical papers; these schemes usually differ 

 mainly in the method of indicating the "series" or "fam- 

 ilies." In Jennings' (1916, p. 415) system for asexual 

 reproduction with the animal Difflugia, for instance, each 

 "family" is a pure line descended from one selected indi- 

 vidual; each pedigree number, consequently, begins with 

 a simple number assigned to the Pj individual. Here we 

 have the simplest possible form of pedigree numbering. 

 With the higher plants, however, we need some special 

 provision for cases of crossing, and also some method of 

 distinguishing asexually produced individuals from those 

 produced sexually. 



Belling (1914, pp. 309-10),-^ for Stizolobium crosses, 

 uses for each series the initials of the common names of 

 the parent species (c. g., VL for velvet bean $ X Lyon 

 bean c?) ; this is practicable because the crosses involve 

 only a small number of named forms, themselves appear- 

 ing practically constant. For the same reasons, the Pi 

 plants, and usually the also, are not individually indi- 

 cated in published pedigrees; VL3 is an Fj plant, and 

 VL3-7 or VL-7 an F^ plant. The obvious result of this 

 procedure is a gain in both clearness and brevity of pres- 

 entation. 



Hayes and East (1915, p. 3) use for maize crosses a 

 scheme that resembles Belling 's in its direct indication of 

 the parentage of hybrids. * ' The various races were given 



3 Or see Fla. Agr. Exp. Sta. Report for year 1913, 1914 or 1915. 



