418 THE FERTILISATION OF FLOWERS. [PART III. 
The regular occurrence of self-fertilisation is accounted for by 
the small, solitary, white flowers, and the scantiness of insect-visits 
that this want of conspicuousness leads to. I, like Sprengel also, 
have observed Pieris brassice, L., and P. rape, L., visiting the 
flowers ; after once resorting to the plant they came frequently. 
Bees and Syrphide also visit the plant (590, IT.). 
Lithospermum canescens, Lehm.—The flowers either are 
heterostyled or are very variable (167), 
Batschia (Iithospermum) longifiorum, Pursh., has cleistogamic 
flowers (167). 
310. EcHIUM VULGARE, L.—The flowers ‘of this plant are 
very conspicuous, and are peculiar in causing insects of very 
Fic. 141.—Echium vulgare, L 
1.—Older flower, from the side. The flower should be represented horizontal. 
2.—Transverse section through the base of a flower, niore magnified. 
k, sepal; bl, corolla; st, stamen; g, style; n, stigma; h, entrance to the honey. 
various sizes to perform cross-fertilisation, both in reaching the 
honey and in carrying off the pollen. 
The honey, which attracts most visitors, is secreted by the fleshy 
base of the ovary, and lies in the base of the five-toothed, funnel- 
shaped corolla. The narrow end of the tube is inclined obliquely 
upwards, and the expanded bases of the five stamens adhere 
to its inner wall for a distance of 4 mm. When the stamens 
become free from the expanded corolla, the latter suddenly widens 
out, and its superior wall extends obliquely upwards for about 
12 mm. farther; the sides, slightly diverging, extend for 9 mm. ; 
and the inferior wall extends for 6 mm., lying horizontally and 
curving slightly downwards near the mouth. The corolla is large 
