CHAP. III. CROSSED AND SELF-FERTILISED PLANTS. 85 



turned out of their pots into the open ground they were planted 

 at a moderate distance apart, so that they were exposed to much 

 less severe competition than in the last case. The longest leaves 

 on the three crossed plants, when turned out, exceeded those on 

 the self-fertilised plants by a mere trifle, viz., on an average by 

 17 of an inch. When fully grown the three crossed plants 

 produced twenty-six flower-stems ; the two tallest of which on 

 each plant were on an average 54*04 inches in height. The 

 three self-fertilised plants produced twenty-three flower-stems, 

 the two tallest of which on each plant had an average height of 

 46'18 inches. So that the difference between these two lots, 

 which hardly competed together, is much less than in the last 

 case when there was moderately severe competition, namely, as 

 100 to 85, instead of as 100 to 70. 



The Effects on the Offspring of intercrossing different Flowers on 

 the same Plant, instead of crossing distinct Individuals. A fine 

 plant growing in my garden (one of the foregoing seedlings) was 

 covered with a net, and six flowers were crossed with pollen from 

 another flower on the same plant, and six others were fertilised 

 with their own pollen. All produced good capsules. The seeds 

 from each were placed in separate watch-glasses, and no difference 

 could be perceived by the eye between the two lots of seeds ; 

 and when they were weighed there was no difference of any sig- 

 nificance, as the seeds from the self-fertilised capsules weighed 

 7 '65 grains, whilst those from the crossed capsules weighed 

 7' 7 grains. Therefore the sterility of the present species, when 

 insects are excluded, is not due to the impotence of pollen 

 on the stigma of the same flower. Both lots of seeds and seed- 

 lings were treated in exactly the same manner as in the previous 

 table (XXIII.), excepting that after the pairs of germinating seeds 

 had been planted on the opposite sides of eight pots, all the 

 remaining seeds were thickly sown on the opposite sides of Pots IX. 

 and X. in Table XXIV. The young plants during the following 

 spring were turned out of their pots, without being disturbed, 

 and planted in the open ground in two rows, not very close 

 together, so that they were subjected to only moderately severe 

 competition with one another. Very differently to what occurred 

 in the first experiment, when the plants were subjected to 

 somewhat severe mutual competition, an equal number on each 

 side either died or did not produce flower-stems. The tallest 

 flower-stems on the surviving plants were measured, as shown in 

 the following table : 



