PART III. | THE MECHAN ISMS OF FLOWERS. 119 
proboscis, it might easily accomplish self-fertilisation. Delpino 
saw V. tricolor visited by Anthophora pilipes. Darwin found it 
visited by Bombus sp. and Rhingia rostrata. 
| I have found V. tricolor, var. arvensis, to be very sparingly 
_ visited, chiefly by bees and humble-bees, more rarely by Rhingia 
and by butterflies (590, I1.). 
q Viola calcarata, L., greatly surpasses V. tricolor in the size 
of its flower and the length of its spur (13 to 25 mm.). It is 
| fertilised only by Lepidoptera, chiefly by Macroglossa _ stella- 
| tarwm (25 to 28 mm.); our quickest worker. I have seen this 
insect visit 194 flowers on different plants in 6? minutes, and I 
could see it cross-fertilise them by means of the tip of its proboscis 
dusted with white pollen (609). 
Viola cornuta, according to Mr, W. E,. Hart (308), is adapted 
_ for fertilisation by nocturnal Lepidoptera by its long spur and by 
_ emitting its perfume most powerfully by night. He found it visited 
by humble-bees, by Hipparchia Janira, and by Cucullia umbratica. 
Viola arenaria, D.C., is visited by butterflies (609). 
Viola biflora, L., is adapted for fertilisation by Diptera (609). 
47, VIOLA opoRATA, L.—Here the end of the pistil which 
bears the stigma is not globular and close to the lower petal, but 
| stands ata short distance from the latter and is bent downwards 
| into a hook. When a honey-seeking insect thrusts its head or 
proboscis beneath the stigma it pushes up the pistil and opens 
} t the conical ring of anthers; the pollen is thus shed upon the 
inserted organ. Thus in every flower the insect touches first the 
_ stigma and then causes shedding of the pollen. 
ba Sprengel’s experiments led him to the conclusion that if insects 
i are excluded the flowers bear no seed. 
: t Visitors : A. Hymenoptera—Apide : (1) Apis mellifica, L. %, very ab., 
's, (as Sprengel described and figured (title-page xi.) it comes downwards and 
inserts its proboscis into the flower from above) ; (2) Anthophora pilipes, 
__F. g, sucks, clinging to the lower petal,—the following species do likewise ; 
(3) Bombus hortorum, L. 9 ; (4) B. lapidarius, L.? ; (5) B. Rajellus, Ill. ¢ ; 
(6) Osmia rufa, L. ¢ 2, very ab., also enters the flower from above as a rule. 
_B. Diptera—Bombylide : (7) Bombylius discolor, Mgn., s. C. Lepidoptera— 
(8) Vanessa urtice, L., s. ; (9) Rhodocera rhamni, L., s. 
48, VIOLA SILVATICA, Fries. (V. silvestris, Lam .).—The spur is 
7 mm. long ; the honey-secreting appendages to the inferior anthers. 
which project into it are 5 mm. long. As in JV. trivolor, the cayity 
