256 Bateson . — The Effect of Cross-Fertilization 
as the pollen is ripe by the time the stigma pierces the ring of 
anthers. The plants used in my experiments were obtained 
from the same locality when still young, and were grown in 
pots. Two capitula on one of the plants were cross-fertilized 
when most of the stigmas were extended, by rubbing over 
them a capitulum of another plant which was covered with ripe 
pollen. This method of crossing is very rough, but the crossing 
of all the florets would not be any better ensured by attempting 
to cross each one individually. The plant from which pollen 
was taken for crossing was a weaker plant than the one with 
which it was crossed. Two capitula on the same plant were 
marked for self-fertilization, and these were allowed to fertilize 
themselves, and were not artificially self-fertilized. This plant 
was not covered by a net, though it would have been better to 
have been so. When ripe the capitula were gathered, and 
there was found to be a considerable difference in the fecundity 
of the cross and self-fertilized capitula. The two self-fertilized 
capitula contained between them 6 9 seeds and 42 sterile ovules ; 
whilst the two cross-fertilized capitula contained between them 
125 seeds and only 8 abortive ovules. 
The seeds from the two lots were allowed to germinate, 
and the seedlings were planted out in pairs on the opposite sides 
of pots, which were so placed as to have the plants of the two 
sides exposed equally well to light. The self-fertilized 
seeds germinated slightly before the cross-fertilized ones. 
When full-grown the plants of both sides were measured, and 
the result is shown in the table opposite. 
The figures in columns D, E, and F show that with only 
three exceptions the crossed exceeded the self-fertilized plants 
in height, besides which the tallest crossed plants were 
decidedly higher than the tallest self-fertilized ones. The 
total height of all the crossed is to the total height of all the 
self-fertilized plants as 100 to 87. When weighed the two 
lots showed hardly any difference, the weight of the crossed 
plants being 108*7 grms., and the weight of the self-fertilized 
105*5 grms., or as 100 to 97. In fecundity the crossed plants 
showed an advantage over the self-fertilized, the average 
