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64 MENDELISM chap. 



tails, bushes, Cupids of the procumbent type like the orig- 

 inal Cupid parent, and Cupids with the compact upright 

 Bush habit (PI. II., 4). These four types appeared in the 

 ratio 9:3:3:1, and this, of course, provided the clue to 

 the nature of the case. The characters concerned are (i) 

 long internode of stem between the leaves which is domi- 

 nant to short internode, and (2) the creeping procum- 

 bent habit which is dominant to the erect bush-like habit. 

 Of these characters length of internode was carried by the 

 Bush, and the procumbent habit by the original Cupid 

 parent. The bringing of them together by the cross 

 resulted in a procumbent plant with long internodes. 

 This is the ordinary tall sweet pea of the wild Sicilian type, 

 reversion here, again, being due to the bringing together 

 of two complementary factors which had somehow be- 

 come separated in the course of evolution. 



To this interpretation it may be objected that the or- 

 dinary sweet pea is a plant of upright habit. This, how- 

 ever, is not true. It only appears so because the conven- 

 tional way of growing it is to train it up sticks. In reality 

 it is of procumbent habit, with divergent stems like the 

 ordinary Cupid, a fact which can easily be observed by 

 anyone who will watch them grow without the artificial 

 aid of prepared supports. 



The cases of reversion with which we have so far dealt 

 have been cases in which the reversion occurs as an im- 

 mediate result of a cross, i.e. in the Fi generation. This is 



