222 THE FERTILISATION OF FLOWERS. [PART III. 
dehisce while still bent down below the stigma, whose edge they 
come in contact with when they afterwards rise up. 
Visitors: A. Diptera—Hmpide: (1) Empis livida, L. s. ; (2) E. rustica, 
Fallen, s. Also numerous small gnats, licking honey. B. Hymenoptera— 
Apide: (8) Andrena parvula, K. 9, s. OC. Coleoptera—WNitidulide: (4) 
Meligethes, lh. See also No. 590, II. 
129. PRuNus pomesTicA, L., P. avium, L., and P. Cerasus, L. 
—Anthers and stigmas ripen simultaneously, and spread apart out 
of the flower; the stigmas overtop the inner stamens but stand 
on a level with the outer ones. Cross-fertilisation is favoured by 
the likelihood of insects touching the stigma and anthers with 
different parts of their bodies while sucking the honey secreted by 
the receptacular tube. Insects collecting or feeding on pollen must 
lead to self-fertilisation and cross-fertilisation indiscriminately. In 
flowers obliquely placed, pollen may readily fall from the taller 
anthers upon the stigma. 
Visitors: A. Hymenoptera—Apide: (1) Apis mellifica, L. 2, 8. very 
ab. ; (2) Bombus lapidarius, L. 2 ; (3) B. terrestris, L. 9; (4) B. hortorum, 
L. 9, all three sucking ; (5) Osmia rufa, L. 9 ¢, s., ab. ; (6) O. cornuta; 
Latr. 9 ¢, s.; (7) Andrena fulva, Schr. 9, s. and c.p.; (8) A. albicans, 
K. 9 g, epand s.; very ab. B. Diptera—Syrphide: (9) Rhingia rostrata, 
L., s., ab.; (10) Eristalis tenax, L.; (11) E. arbustorum, L., s. C. Lepi- 
doptera—Rhopalocera: (12) Pieris brassice, L.; (13) P. rape, L. ; (14) P. 
napi, L., all three sucking. See also No. 590, 11. 
Tribe Spirwe. 
130. SPIRHZA ULMARIA, L.—The flowers contain no honey but 
a great quantity of pollen. The stamens at first arch over towards 
the middle of the flower, so as to cover the stigmas completely ; 
they gradually become erect and incline outwards in centripetal 
succession, and the anthers then dehisce, covering themselves all 
round with pollen. When the stamens have risen up, the centre 
of the flower becomes the most convenient place both for small 
insects to settle on, and for larger insects traversing the inflorescence 
to step upon. Cross-fertilisation is thus readily performed, but 
self-fertilisation is also very liable to occur. 
The crowded inflorescences not only attract numerous insects 
but also lead to great economy of time in the process of fertilisation. 
In the absence of insects, self-fertilisation almost always takes 
