494 THE FERTILISATION OF FLOWERS. [PART II]. 
above this, the tube suddenly widens, forming a pouch anteriorly, 
and its direction changes, becoming parallel to the stem. 
Very many short-lipped insects, especially flies and small bees, 
which are too small to effect cross-fertilisation, are thus excluded ; 
for Lamiwm album, like so many of our native flowers with tubes 
10 to 20 mm. long, is specially adapted for humble-bees and other 
large bees. The following characters of the corolla exemplify this. 
The erect part of the tube, which is 7 mm. long, is followed by the 
division of the tube into a bilobed lower lip (6, 1) which serves as 
a landing-place, two erect lateral lobes (¢, 1) which admit the bee’s 
head between them and are continued directly upwards from: the 
side-walls of the tube, and the horizontal vaulted upper lip (e, 1) 
which serves to shelter the anthers (f, 1) and the stigmas (g, 1) 
immediately-below it. The small appendages of the lateral lobes 
Fic. 167.—Lamium album, L. 
1.—Flower. from the side. 
2.—Ditto, after removal of the calyx. 
3.—Ovary and nectary (xX 7). 
4.—Tip of the style (x 7). , : : 
a, nectary ; b, under lip; ¢, side-lobes which receive the bee’s head between them; 
d, functionless appendages ; e, upper lip; f, anthers; g, lower division of the style. 
(c, 1) are functionless rudiments of the primitive five-lobed corolla. 
One of the divisions of the style which lies above or between the 
anthers lies in the same straight line with the style; while the 
other, a little shorter, bends downwards almost at right angles, so 
that its stigmatic tip projects below the anthers (4, Fig. 167). 
Cross-fertilisation is therefore induced, not by dichogamy, but by 
the position of the stigma. In absence of insects, self-fertilisa- 
tion may take place, but it is doubtless rare, for the flowers are 
plentifully visited by bees. 
We can estimate by direct observation how perfect the 
adaptation of this flower is to bees’ visits. The bee alights on 
the under lip, and in doing so thrusts its head between the broad 
lateral lobes of the mouth, clings with its forefeet to the base 
