Chap. II. CEOSSED AND SELF-FERTILISED PLANTS. 



20 



receives some pollen. The number of seeds produced 

 by the crossed and self-fertilised flowers differed very- 

 little. 



Crossed and self-fertilised seeds obtained in the above 

 manner were allowed to germinate on damp sand, and as often 

 as pairs germinated at the same time they were planted in the 

 manner described in the Introduction, on the opposite sides of 

 two pots. Five pairs were thus planted ; and all the remaining 

 seeds, whether or not in a state of germination, were planted on 

 the opposite sides of a third pot, so that the young plants on 

 both sides were here greatly crowded and exposed to very 

 severe competition. Eods of iron or wood of equal diameter 

 were given to all the plants to twine up; and as soon as one of 

 each pair reached the summit both were measured. A single 

 rod was placed on each side of the crowded pot, No. III., and 

 only the tallest plant on each side was measured. 



Table I. (First Generation.) 



The average height of the six crossed plants is here 86 inches, 

 whilst that of the six self-fertilised plants is only 65*66 inches, 

 so that the crossed plants are to the self-fertilised in height as 

 100 to 76. It should be observed that this difference is not due 

 to a few of the crossed plants being extremely tall, or to a few of 

 the self-fertilised being extremely short, but to all the crossed 

 plants attaining a greater height than their antagonists. The 

 three pairs in Pot I. were measured at two earlier periods, and 

 the difference was sometimes greater and sometimes less than that 



