 parrius) THE MECHANISMS OF FLOWERS. 196 
) A. Hymenoptera—A pide : (1) Bombus lapidarius, L. 9 $, sometimes s., 
- sometimes c.p.; (2) B. terrestris, L. 9, s.; (3) Andrena atriceps, K. 2 ¢,s.; 
(4) A. albicans, K. 2, c¢.p.; (5) A. xanthura, K. 2, c.p.; (6) Apis mellifica, 
L. $,¢p., very ab. B. Lepidoptera—Noctue: (7) Plusia gamma, L., s., freq: 
©. Coleoptera—Nitidulide: (8) Meligethes, creeping about within the 
- flowers. 
Cytisus sagittalis, Koch, is visited by bees only ; I have noted 
- eight different species upon its flowers (590, I1.). 
In Cytisus canariensis, L., and C. albus, Link., according to 
Hildebrand, the carina bends down slightly under pressure, and 
the anthers and style first move slightly downwards with it, and 
then spring upwards so that the pollen flies out and part of 
it is applied without fail to the stigma (No. 346). It is, however, 
hardly conceivable that such an action effected by insects should 
lead only to self-fertilisation. 
_ 112. Cytisus (SAROTHAMNUS) scopARIUS, Koch.—The flowers, 
_ like those of our species of Genista, are explosive and devoid of honey. 
| Darwin noticed that the flowers do not explode spontaneously, and 
_ scarcely set a single capsule if protected from insects; but that 
when an insect visits the flower, first the short stamens explode, dust- 
ing it with pollen below, then the longer stamens, dusting it above, 
and that finally the pollen applied to the under side of the insect 
_ by the shorter stamens fertilises those stigmas which are not 
_ covered with pollen at the moment of explosion. 
__ I have observed the way in which insects operate on the flower 
most closely in the case of the hive-bee. The bee, on alighting, 
_ grasps the alz with its mid and hindlegs, thrusting its forelegs and 
_ head below the middle of the vexillum. The ale and with them 
‘the carina are thus pressed forcibly down, and the united upper 
+3 “margins of the carina split asunder from behind forwards. [The 
alze are connected with the carina by means of a fold ( jf; 4b) which 
Biches j in the angle between the upper edge of the carina and the 
“sharp pouched protuberance at its side (7; 4, 4c, 6)]. As soon as 
I ithe split has extended midway, the five shorter stamens spring out ; 
_ they had dehisced in the bud, pressing their pollen against the 
closed upper edge of the carina (5, Fig. 65), and now they force 
} ip of their pollen against the under side of the bee. The shock 
- not enough to drive the bee away; at most it pauses for a 
‘moment, and then resumes work with increased diligence. The 
we ‘split now quickly extends further, and it has scarcely reached the 
place where the tip of the style lies than a second and much 
| E ; 0 2 
-e 
