KNOWLEDGE OF HEREDITY IN PISTJM. 101 



described in terms of the following five pairs of allelo- 

 morphs :— 



Dominant Alielomorph. Recessive Allelomorph. 



Gray testa ; coIoTored leaf- Absence of pigment, except 



axils (red in the absence chlorophyll and allied 



of P) ; and coloiu*ed flowers substances, in petals, axils, 



(red in absence of P) . . C and testas . . c 



Marked spotting of some Spotting 



shade of purple on the very famt 



testa . . S or absent . , s 



Maple marking present . . M Maple marking absent . . m 



Presence of factor modifying 



red pigment to pmple . . P Piirple factor absent . . p 



Dark hylum . . D Pale hyliim . . d 



In the case of the appearance of plants having coloured 

 flowers but green axils, as described by Tschermak (19), a 

 sixth factor must be introduced, but no such plants appeared 

 among the writer's experiments. 



S and P are always quite invisible (masked) in the absence 

 of C ; and M, as before stated, is very nearly invisible when C 

 is absent. 



The observed phenomena are readily understood by sup- 

 posing each of the above five pairs of allelomorphs to segregate 

 according to the ordinary Mendelian rule. So far as is known, 

 the segregation of each pair is quite independent of that of all 

 the others, but the figures available are not sufficient to exclude 

 absolutely the possibility of some partial coupling. There is 

 no definite indication, however, that anything of the kind 

 takes place. 



The phenomena thus interpreted are briefly as follows : — 



(i.) All combinations of characters possible on the above 

 hypotheses, and.no others, have been observed. 



(ii.) Mendel's simple case is represented by the segregation 

 of the pair of allelomorphs C-c, P being also present in both 

 parents. 



(iii.) Data have already been published with regard to the 

 characters S and M (13, 14, 15). The results of crossing 

 heterozygote plants with recessives were as follows : — 



S. s. M. m. 



Number of offspring . . 21 23 . . 25 29 



7(6)08 (13) 



