58 MENDELISM chap. 



its habit of growth. The numerous stems do not 

 diverge from one another, but all grow up side by 

 side giving the plant the appearance of a compact 

 bush (PI. 1 1., I ). Under ordinary conditions it attains 

 a height of 31-4 feet. A number of crosses were 

 made between the Bush and Cupid varieties, with 

 the somewhat unexpected result that in every 

 instance the .F^ plants showed complete reversion 

 to the size and habit of the ordinary tall sweet- 

 pea (PI. II., 3), which is the form of the wild plant 

 as it occurs in Sicily to-day. The F^ generation from 



Bush X Cupid 



I 

 Tall - - Fi 



I 1 ' 1 1 



Tall Bush Cupid Cupid F^ 



(procumbent) (erect) 

 (9) (3) ' (3) (') 



these reversionary tails consisted of four different 

 types, viz. tails, bushes, Cupids of the procumbent 

 type like the original Cupid parent, and Cupids 

 with the compact upright Bush habit (PI. II., 4). 

 These four types appeared in the ratio 9:3:3: i , 

 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 

 dominant to short internode, and (2) the creeping 

 procumbent habit which is dominant to the erect 

 bush-like habit. Of these characters length of inter- 

 node 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 pro- 



