368 PLANTS FERTILE WITHOUT INSECT-AID. Chap. X, 



are incessantly visited by hive and humble-bees. When 

 insects were excluded the flower-heads seemed to produce as 

 many and as fine seeds as the exposed heads. 



T. procumbens. On one occasion covered-up plants seemed to 

 yield as many seeds as the uncovered. On a second occasion 

 sixty uncovered flower-heads yielded 9 ' 1 grains weight of 

 seeds, whilst sixty heads on protected plants yielded no less 

 than 17 "7 grains; so that these latter plants were much 

 more productive; but this result I suppose was accidental. 

 I have often watched this plant, and have never seen the 

 flowers visited by insects ; but I suspect that the flowers of 

 this species, and more especially of Trifolium minus, are 

 frequented by small nocturnal moths which, as 1 hear from 

 Mr. Bond, haunt the smaller clovers. 



Medicago lupulina (Leguminosre). On account of the danger of 

 losing the seeds, I was forced to gather the pods before they 

 were quite ripe ; 150 flower-heads on plants visited by bees 

 yielded pods weighing 101 grains; whilst 150 heads on 

 protected plants yielded pods weighing 77 grains. The 

 inequality would probably have been greater if the mature 

 seeds could have been all safely collected and compared. 

 Ig. Urban (Keimung, Bluthen, &c, bei Medicago, 1873) has 

 described the means of fertilisation in this genus, as has the 

 Eev. G. Henslow in the ' Journal of Linn. Soc. Bot.' vol. ix. 

 1866, pp. 327 and 355. 



Nicotlana tabucum (Solanacese). Fully self-fertile. 



Ipomcea purpurea (Convolvulacese). Highly self-fertile. 



Leptosiplion androsaceus (Polemoniacese). Plants under a net 

 produced a good many capsules. 



Primula mollis (Primulacese). A homomorphic species, self-fer- 

 tile: J. Scott, in' Journal Linn. Soc. Bot.' vol. viii. 1864, p. 120. 



Nolana prostrata (Nolanacese). Plants covered up in the green- 

 house, yielded seeds by weight compared with uncovered 

 plants, the flowers of which were visited by many bees. 

 in the ratio of 100 to 61. 



Ajuga reptans (Labiatae). Set a good many seeds ; but none of 

 the stems under a net produced so many as several un- 

 covered stems growing closely by. 



Euphrasia officinalis (Scrophulariacese). Covered-up plants pro- 

 duced plenty of seed ; whether less than the exposed plants I 

 cannot say. I saw two small Dipterous insects (Dolichcpos 

 nigripennis and Empis chioptera) repeatedly sucking the 



