CHAP. IIL VEBBASCUM THAPSUS. 89 



two lots of seedlings were not subjected to any mutual competi- 

 tion. Three of the crossed plants when in full flower were 

 measured, but no care was taken to select the tallest plants ; 

 their heights were 7f, 7|, and 6| inches; averaging 7 '08 in 

 height. The three tallest of all the self-fertilised plants were 

 then carefully selected, and their heights were 6|, 5f , and 5|, 

 averaging 5 '75 in height. So that the naturally crossed plants 

 were to the spontaneously self-fertilised plants in height, at 

 least as much as 100 to 81. 



VEBBASCUM THAPSUS. 



The flowers of this plant are frequented by various insects, 

 chiefly by bees, for the sake of the pollen. H. Miiller, however, 

 has shown ('Die Befruchtung,' &c. p. 277) that F. nigrum 

 secretes minute drops of nectar. The arrangement of the re- 

 productive organs, though not at all complex, favours cross- 

 fertilisation; and even distinct species are often crossed, for a 

 greater number of naturally produced hybrids have been observed 

 in this genus than in almost any other.* Nevertheless the 

 present species is perfectly self -fertile, if insects are excluded ; 

 for a plant protected by a net was as thickly loaded with fine 

 capsules as the surrounding uncovered plants. V&rbascum 

 lychnitis is rather less self-fertile, for some protected plants did 

 net yield quite so many capsules as the adjoining uncovered 

 plants. 



Plants of F. thapsus had been raised for a distinct purpose 

 from self- fertilised seeds ; and some flowers on these plants were 

 again self-fertilised, yielding seed of the second self-fertilised 

 generation ; and other flowers were crossed with pollen from a 

 distinct plant. The seeds thus produced were sown on the 

 opposite sides of four large pots. They germinated, however, so 

 irregularly (the crossed seedlings generally coming up first) 

 that I was able to save only six pairs of equal age. These when 

 in full flower were measured, as in the following table (XXV.). 



"We here see that two of the self-fertilised plants exceed in 

 height their crossed opponents. Nevertheless the average height 

 of the six crossed plants is 65 '34 inches, and that of the six 

 self- fertilised plants 56 -5 inches ; or as 100 to 86. 



* I have given a striking case found growing wild : ' Journal of 

 of a large number of such hybrids Linn. Soc. Bot.' vol. x. p. 451. 

 between F. thapstu and lychnitis 



