PART IIL] THE MECHANISMS OF FLOWERS. | 417. 
bright blue limb of the corolla expands to a diameter of 15 to 18 
mm. The connective has no terminal appendage ; otherwise the 
flower resembles that of Myosotis, and self-fertilisation is likewise a 
regular occurrence. 
Visitors : Hymenoptera—Apide: (1) Bombus terrestris, L. 9, s. ; (2) 
Osmia rufa, L. ¢, s.° 
309. LITHOSPERMUM ARVENSE, L.—The smooth ovary secretes 
a small amount of honey, which lies in the base of the corolla; the 
latter forms a tube 4 to 5 mm, long, and only 1 mm. wide in its 
lowest part.. The five short stamens are inserted upon the corolla 
below its middle, and their anthers dehisce inwards longitudinally 
Fic. 140.—Lithospermum arvense, L. 
1.—Tip of style, from a bud (x 36). st, stigma, 
2.—Position of essential organs in the flower. 
and let their pollen escape, before the opening of the flower. The 
_ style, which is 2 mm. long, ends in two smooth, rounded lobes, and 
_ bears immediately below these an annular ridge covered with stig- 
| matic papille ; this stands on a level with the anthers, completely 
filling up the narrow passage to the base of the flower. The upper 
_ ends of the stamens curve slightly outwards, thus guiding an insect’s 
_ proboscis to the centre of the flower and causing e to pass between 
_ the anthers and stigma. Ifin the young flower an insect thrusts in 
_ its proboscis, already dusted with pollen, cross-fertilisation takes 
place, and the proboscis gets dusted at the same time with fresh 
pollen. But as the pollen issues more and more from the anthers, 
e -cross-fertilisation is soon rendered more difficult, and ultimately 
_ self-fertilisation becomes unavoidable. 
