JOimNAL OF TTTI'^- ROYATi nORTTOTTTiTlinATj 8()('I^V^^ . 



It will be observed that ibo various ivlnlioiis and iniernciions 

 between the five factors in the case of i\\c snn ptlragon are pmi icniarly 

 interesting and suggestive. The faclors 1, L, T, and 1) cmi only be 

 manifested in Ihc pi-cstMu-i- of Y. in tJie absence of Y tho (lowers are 

 pure white, while ni ihe picsence of Y all are colom'ed. I with Y gives 

 ''ivory.'" L with Y gives "crimson," but with I in addition it 

 gives "magenta." T and D can only be manifested in the presence 

 of L. 



In order to show the simple effects of the presence and absence of the 

 five factors and their somewhat complicated relations and interactions 

 only a single presence of each factor is shown in the table. In accord- 

 ance with INFFvnFr.'s Inw, however, it will be quite understood that a 

 pure-bred foiiu \\t)Ml(l linve a doable presence of each factor; thus the 

 pure-breeding wild form would be constituted YYIILLTTDD and so 

 on with the others. Miss Wheldale found that the single presence 

 of these five factors gave the same visible result as the double presence, 

 except that the single presence of L gave a lighter shade of ' * magenta 

 than the double presence. 



The breeding results from the single presence and the double pre- 

 sence would, of course, be quite different. All the above combinations 

 of factors maj^ occur wdth either a double presence or a single 

 presence of each factor in various combinations, in accordance with 

 Mendel's law. 



In the course of her experiments Miss Wheldale has incidentally 

 cleared up certain difficulties in regard to the form known in gardens as 

 ' White Queen. ' This form has apparently pure white lips and tube, 

 with a yellow palate. Nevertheless, Miss Wheldale 's experiments 

 demonstrate conclusively that in breeding it behaves precisely as if it 

 were an ivory, the yellow form extracted from it in the second genera- 

 tion being rather paler in shade than the ordinary yellow.'^ 



Unit-Factoes in the Sweet Pea (Lathyrus odoratus). 



The sweet pea has been specially investigated by Peofessor 

 Bateson, Miss Saundees, and Me. Punnett. So far at least twelve 

 unit factors have been found which determine the habit of growth, 

 flower form, and colour. All these factors are evidently present in 

 the typical wild sweet pea, which has a tall and prostrate habit, with 

 dark leaf axils; the flowers have an erect purple standard, with blue 

 wings, the anthers are fertile, and the pollen grains are long. 



Eight of these factors may be represented as follows : — 



T representing tallness of growth. 



P representing prostrate habit of growth. 



W representing whiteness in the flower. 



C representing first sap-colour factor. ) ^ , , . n 



T» .• 1 1 p J h Red colour m the flower. 



R representmg second sap-colour factor. J 



* Cf. Feport of Int. Covf. of Genetics, 1906, p. 117. 



