oe a gy eS 
PART IIL. | THE MECHANISMS OF FLOWERS, 491 
its proboscis through the narrow passage between the lower ends 
of the outer filaments, cannot avoid touching the lower and shorter 
arms of the levers; and the long arms at once bend down, bringing 
the anthers in contact with the bee’s back. The median pair of 
stamens only become free a little below the hood of the upper lip, 
and their anthers are only touched by large humble-bees. The 
flower is distinctly proterandrous. 
The fertilisers are almost exclusively humble-bees (609). 
356. GALEOPSIS TETRAHIT, L.—The tissue below the ovary 
expands into a nectary which surrounds the two anterior divisions 
Fic. 166, 
1—3.—Galeopsis Tetrahit. 
1.—Flower, from the front. 
2.—Its essential organs, from the front (x 7). 
3.—Ovary and nectary (x 7). 
4—6.—G. ochroleuca. 
4.—Position of the reproductive organs when the flower expands. 
5.—Ditto, when it withers. 
6.—Ovary and nectary. 
of the ovary. The honey is lodged in the lower, smooth portion of 
the tube, which ascends obliquely and is of very variable length in 
different plants. In the cases which I examined it varied from 11 
to1l7 mm. Fora space of 4 to 6 mm. at its upper part, this tube 
is wide enough to admit the whole head of a small humble-bee, or 
at least the front half of that of a large one ; so that large humble- 
bees with a proboscis not less than 14 to 15 mm, long, and small 
ones with a proboscis 12 mm. long, can reach the base of the tube in 
the largest varieties of G. Tetrahit. The corolla divides above into a 
vaulted upper lip which covers the anthers, and a trilobed under lip 
which serves as a landing-place ; the under lip bears guiding-marks, 
and is modified to facilitate the imtroduction of the bee’s head. 
