HOWARD, HOWARD AND ABDUR RAHMAN. 303 



It will be evident that the environment may modify to a con- 

 siderable extent the usual pollination mechanism in a crop. In 

 Northern Europe cross-poUination in wheat is a rare occurrence, in 

 warmer climates it is more frequent while in hot dry localities such 

 as the Canal Colonies of the Punjab where the crop can only be 

 grown by means of artificial irrigation, cross-poUination is quite 

 common. 



2. Barley. 

 A large number of pure line cultures of barley, belonging to 

 different varieties, have been grown at Piisa, but no cases of natur- 

 al crossing have so far been observed. Natural crossing, how- 

 ever, occurs sparingly in this crop as Rimpau' found six cases 

 in eight years. 



3. Peas. 



In India, as in Europe, the cultivators recognise two great 

 groups of cultivated peas — purple flowered peas {Pisum arvense, L., 

 known in India as kerao) and white flowered peas {Pisinn 

 sativum, L., known as mattar). 



It is generally understood in Europe that in both these groups 

 self-poUination is the rule and that natural cross-fertilization 

 does not take place. ^ Two cases of undoubted natural cross- 

 fertilization have been proved at Piisa between Indian forms of the 

 purple and white flowered groups. 



In the case of kerao, 28 plants were selected from the harvest 

 of 1909 and sown separately the following October. In 27 cases 

 the progeny was uniform but in one instance splitting took place. 

 Some plants had uniformly green leaves, others were reddish on the 

 margin. Late and early and small and large seeded plants oc- 

 curred. Seven plants had seeds with black spots only, two plants 

 had seeds with black and brown spots. In this case crossing 



1 'Rimj>SLU, La}idwirtschajtliche Jafirbiicher, lid. XX, 1891, s. 3o7. 



2 See FrutoirtJi, Die Zuchhaig, Bd. Ill, 1008, s. 13r> ; Lock, Annals Roijal Botanic Gardens, 

 Peradeniyu, Vol. II, 1904-05: Rimpau, Land. Jahrbucher, 1891, s. 366 and TBcliermnk Zcit, 

 f. d. land. Verxuchswesen in Oesterreich, Bd. Ill, 1900, e. 173. 



