PART IIT. | THE MECHANISMS OF FLOWERS. 201 | 
side. The carina alone forms the platform for insects to alight ve 
i and the lever by which its own downward rotation is effected: 
H own elasticity brings it back to its former position on removal ie 
the pressure. 
Cross-fertilisation is insured, in case of insect-visits, by the 
prominence of the stigma, which must touch the under surface 
of an alighting insect in advance of the anthers. In absence of 
insects, self-fertilisation cannot occur, especially as the style con- 
tinually grows, so that in older flowers it protrudes for a distance 
of 1 to 14 mm. beyond the carina. The brightly coloured flowers, 
‘massed in racemes, attract numerous insects. The calyx-tube is 
only 2 to 3 mm. long; the broad vexillum ascends at a very small 
angle from the horizontal, and is the better fitted to serve as a 
fulerum against which the bee may place its head while thrusting 
down the carina with its legs. Both honey and pollen are thus 
rendered accessible to short-lipped bees. In sunny weather the 
flowers are the resort of so many insects that they can well 
afford to dispense with the power of self-fertilisation. 
~ Visitors: A. Hymenoptera—Apide: (1) Apis mellifica, L. 9 (6), s. and 
 ©.p. ; so abundant as to make nine-tenths of all the visitors ; (2) Bombus senilis, 
| Sm. 2 (14—15) ; (8) B. silvarum, L. 9 (12—14) ; (4) B. agrorum, F. 9 (12— 
15) ; (5).B. confusus, Schenck, 2 (12—14) ; (6) B. terrestris, L. 2 (7—9) ; (7) 
_ B. muscorum, F. 9 § (10—14) ; (8) B. pratorum, L. 9 § (8—11}); (9) B 
Scrimshiranus, K. §:—all sometimes suck honey, sometimes collect pollen ; 
~ (10) B. (Apathus) rupestris, F. 9 (12—14), s.; (11) B. campestris, Pz. @ 
~ (10—12), s. ; (12) Eucera longicornis, L. ¢ 9 (10—12), s. and cp. ; (13) An- 
drena labialis, K. 9 ¢, s. and e.p.; (14) A. nigroswnea, K. ¢ (3); (15) 
_ Halictus albipes, F. 2 (3), s. and cp. ; (16) H. flavipes, F. 2, s. and c.p. ; (17) 
H. lugubris, K. 9; (18) Megachile circumcincta, K. 9, s. and e.p.; (19) 
Osmia aurulenta, Pz. 9 (8—9), s. and ce (Thur.) ; (20) O. spinulosa, K. 9 
(Thur.) ; (21) Chalicodoma muraria, F. 2 (10), s. and ep. (Thur.) ; (22) 
Ceelioxys conoidea, Ill. 9,8. B. Diptera—Syrphide : (23) Volucella plumata ; 
mi—8). ©. Lepidoptera—i(a) Rhopalocera: (24) Pieris napi, L., s.; (25) 
yeeena sp. ; (b) Sphinges : (26) Zygeena carniolica, Scop. (Thur.) ; (¢) Noctue : 
_ (27) Euclidia glyphica, L.; (28) Plusia gamma,:L., ab.,—all sucking, but 
apparently not effecting fertilisation. See also No. 590, 1 
: 
= 
re 
Stylosanthes, Swartz, Arachis, L., Heterocarpea, Phil., Lesperdeza, 
Rich., and Chapmannia, Torr. nid’ Gr., have cleistogamic Howers 
} -ac Biding to Kuhn. 
_ £rrum lens, L., is visited by the honey-bee and by Lepidoptera 
(590, 11.). 
Vicia hirsuta; Koch, is remarkable for the great simplification 
of the whole mechanism of the flower, in relation to its great 
_ reduction in size (590, II). 
