PART III. | THE MECHANISMS OF FLOWERS. 461 
the hindmost are the longest, as they might easily escape being 
touched if of the same length with the others. The bee’s pro- 
boscis, entering the flower in the way described above, comes in 
contact immediately afterwards with the sharp processes of the 
anthers; the anther-lobes at once separate slightly at their lower 
and anterior edges, and the fine, dusty pollen is shed upon the 
insect’s proboscis. 
In spite of these manifold adaptations, the plant, from growing 
in shady spots, is, as a rule, sparingly visited by bees ; but in their 
absence self-fertilisation takes place regularly. As in Rhinanthus 
minor, the end of the style curves more and more downwards, and 
at last inwards, so that the stigma comes to lie below the pollen- 
receptacle (5, Fig. 158), which in the old flower opens of itself. 
In flowers whose colour has changed to reddish the stigma is 
always found in this position. 
Visitors : Hymenoptera—A pide : (1) Bombus agrorum, F. § ? ! (10—15), 
sucking normally. Its weight bends down the flowers to which it hangs, It 
first inserts the tip of its proboscis into the upper part of the flower, then 
thrusts the whole proboscis and its head into the tube. After visiting a flower, 
which takes only a few seconds, it almost always flies away to a neighbouring 
plant. (2) B. hortorum, L. % ! (18—20), sucking normally, just as the former 
species (Siebengebirge, July 8, 1871); (3) B. terrestris, L. 2 (7—9), bites 
through the corolla close above the calyx, so that one mandible makes a hole 
on each side of the sharp edge of the corolla, and through one of these two holes 
the bee inserts its proboscis ; (4) B. pratorum, L. § ¢ (8—9), acts similarly 
(Siebengebirge, July 8, 1871) ; (5) Apis mellifica, L. § (6), do., very ab. ; (6) 
Megachile circumcincta, K. 9! (11), sucking normally, only one specimen. 
B. Diptera—Stratiomyide : (7) Oxycera pulchella, Mgn., I saw this species on 
the flowers at Warstein,—it probably could not reach either the honey or 
the pollen. See also No. 590, 11. 
Melampyrum arvense, L., is visited by various insects, but only 
fertilised by very long-tongued humble-bees (590, II). 
Melampyrum nemorosum, L.—The honey is stolen by various 
humble-bees, but the flower is fertilised only by Bombus hortorum, 
L. 8 (590, III.). 
Melampyrum silvaticum, L.—The flower is of small size and its 
mechanism is much simplified (590, II.). 
The six forms above described in which dry pollen is shed on 
the insect-visitor, viz. Odontites lutea, O. serotina, Kuphrasia offi- 
cinalis, Melampyrum, Rhinanthus, and Pedicularis, show remarkable 
gradations in the way in which the anthers are protected and the 
