No. 607] NUMBERING PLANTS IN PEDIGREE CULTURES 433 



two particular individual plants, not of two particular 

 branches as with Citrus. 



Thus with Matthiola a series starts with the crossing, 

 in a given direction, of two apparently uniform seed- 

 reproduced types, while with Citrus a series starts with 

 the crossing of two clons. In another case it might be de- 

 sirable to ignore some evident genetic variation in fea- 

 tures not being studied, and to base the delimitation of 

 the series on genetic differences of seed-reproduced Pj 

 individuals in some particular feature under consideration 

 (e. g., in color characters). 



Fourth, in cases where polyembryony is to be expected 

 nine numbers (1 to 9), instead of one, may be given, so far 

 as needed, to the product of each seed. Thus, with the 

 Citrus cross mentioned above, the first seed will be as- 

 signed the numbers 27aa-ll to 27aa-19, the second seed 

 the numbers 27aa-21 to 27aa-29, etc.*^ The actual plants 

 from the first three seeds are therefore designated as 

 follows : 



Seed Xo. 1 {-1 }.lnnt>). 27aa-ll and 27aa-12. 



Seed Xo. 2 (2 jilaiits), 27aa-21 and 27aa-22. 



Seed Xo. ;^ (1 plant), 27aa-31. 

 If, then, two trees are budded from tree 27aa-31, these 

 will be 27aa-31-a and 27aa-31-b. 



It may be ol)jccted tliat tliis treatment of polyembryony 

 gives mislea^liim- i]innl)c'rs to plants from adventitious em- 

 bryos. It mny. liow i'\ (m-. be impossible in many cases to 

 differentiate ])i)si lively these asexually produced progeny 

 before maturity, if at all without progeny tests, and the 

 probable inapplicability of some of the numbers must be 

 kept in mind. Where, as with crosses of Citrus trifoliata 

 with Eucitrus species, the strictly maternal individuals 

 can be separated at an early stage, they can be discarded ; 

 or, if such plants are to be kept, and their exact origin in- 

 dicated, letters may be used, thus : 



43aa-ll (true hybrid). 



43aa-la (for 43aa 12) I {]A:m\> tVoin adviMititious or 

 43aa-lb (for 43aa l:') , a>rxiially produced (.ml.ryos). 



