432 



THE AMEBIC AN NATUEALIST [Vol. LI 



perhaps a part permanently marked, and noted in the 

 records, because of some somatic mutation. In the same 

 way, a small letter affixed to any individual designation of 

 a plant not in a pedigree culture, such as, for instance, the 

 number of a tree in a field experiment, may be used to 

 indicate a particular branch. A small letter used alone 

 will indicate a "generation" of vegetative propagation; 

 for example, in the case mentioned above, "-51a-a" and 

 ''-51a-b" would be trees budded from the mutant branch 

 "-51a. 



Third, small letters affixed to the series number may be 

 used to designate individuals of the first (or gener- 

 ation of any series, whether hybrid or not.^ The definition 

 of individual would necessarily be determined and re- 

 corded for each type of work; where desired, the "indi- 

 vidual" may be a branch, or even a single bud or fruit. 

 Thus, in my work with Citrus, a letter is assigned to each 

 self-pollinated branch giving seedlings. For example, 

 series 28 consists of descendants of selfed Valencia 

 orange; "28a," then, indicates one bagged branch of 

 Valencia, "28b" another branch, etc. The progeny 

 will be 28a-ll, 28a-12, 281>-32, etc. 



For a hybrid series, on this plan, two letters are used 

 to designate the two parents, the letters being independent 

 of those used in the corresponding non-hybrid series. For 

 example, my Citrus series 27 represents Valencia orange 

 $ X Imperial pomelo ^, and "27aa" designates a cross 

 between two particular branches. 27aa-21, then, will be 

 an Fi hybrid. 



Similarly, in my work with Matthiola mutants, series 

 23 indicates the cross Snowflake ("normal") type $ 

 X Slender type c^. "23ea" designates the combination of 



5 The complete pedigree numbers mi^'lit I 2^;i-:VJ-.- 1 nml -.''.i^-.lla-b 

 (see below). 



