rerur] § THE MECHANISMS OF FLOWERS. 239 
} 151. Pyrus communis, L.—The stamens are here longer than | 
he styles, but when the flower opens they are curled inwards and 
immature, while the stigmas are ripe and project. Cross-fertilisa- | 
tion is insured only if insects come soon after the opening of the 
flower. In absence of insects, self-fertilisation takes place as in 
Pyrus Malus. I have often observed by experiment how easily 
pollen from a ripe stamen adheres to the stigmas of a flower, long 
efore its own anthers are ripe. 
_ Visitors: A. Diptera—(a) Syrphide : (1) Eristalis tenax, L., very ab. ; (2) 
®. arbustorum, L.; (3) E. nemorum, L., ab, ; (4) E. intricarius, L. ; (5) 
| Syritta pipiens, L. ; (6) Ascia podagrica, F., both ab. ; (7) Melanostoma mellina, 
L,, all the Syrphide both s. and f.p. ; (b) Muscide : (8) Anthomyia radicum, 
'R.D. ¢ 9, very ab. ; (9) Pollenia Vespillo, F.; (10) P. rudis, F. ; (11) Musca 
corvina, F, ; (12) M. domestica, L. ; (13) Lucilia cornicina, F. ; (14) Calliphora 
-erythrocephala, Mgn.; (15) Sepsis sp., all s.; (16) Scatophaga merdaria, F., 
‘s. and fp. B. Hymenoptera—(a) Apidw: (17) Apis mellifica, L. $, very 
ab.,s. and c.p.; (18) Bombus terrestris, L. 2, s., scarce, and flying away after 
siting a few flowers ; (19) Andrena albicans, K. ? ¢, ¢.p. and s., ab. ; (20) 
.. Gwynana, K. 2; (21) A. parvula, K. 2 ; (22) A. Collinsonana, K. 9, all 
both s. and ec. P- 5 (23) Halictus rubicundus, Chr. 9, ¢.p. and s. ; (6) Formicide : 
24), Lasius niger, L. %, 1h. ; (c) |Tenthredinide : (25) Dolerus gonager, K1., 
e; (26) Nematus capreee, L., freq., s. C. Coleoptera—(a) Nitidulide : 
27) Meligethes, ab. ; (0) Civculiowides ; (28) Rhynchites squatus, L.; (¢) 
occinellide : (29) Coccinella 14-punctata, L. ; (d) Phalacride : (30) Olibrus 
peus, F., all four licking honey. D. Thysanoptera—(31) Thrips, ab. 
152. Pyrus AucupaRIA, Gert.—When the flower opens, the 
amens are still immature, the outer ones standing erect, the inner 
‘ones bent inwards so that their anthers are placed below the 
igmas. The stigmas are ripe, and project in the centre of the, 
ower. The anthers, which open inwards, cover themselves all | 
‘round with pollen. In cold, dull weather, the innermost anthers — 
jremain bent down below the stigmas even after dehiscence; the 
. : er ones stand above the stigmas, incurved towards them; thus, 
}im absence of insects, self-fertilisation takes place readily. On the 
/ other hand, in warm sunshine, the stamens are inclined away from 
\t e stigmas, and the honey-secreting ring is visible between, 
| protected with hairs issuing from the base of the style. Insects, in 
‘di pping down to the honey, touch stamens and stigmas with 
| Mpposite sides of their heads. The small flowers are rendered 
bi mspicuous by aggregation, and the rich supply of honey attracts 
" ry numerous insects. 
Visitors : A. Hymenoptera—(a) Apide: (1) ae mellifica, L. $,s. and 
. py very ab. ; (2) Andrena albicrus, K. 9 ¢; (3) A. albicans, K. 9, very 
