140 THE FERTILISATION OF FLOWERS. [PART III. 
margins, the stigmas come into close relation or even immediate 
contact, with the pollen-covered anthers. Insects alight as a rule 
upon one of the five outspread petals, and then find that the 
easiest course towards the anthers lies between two groups of 
stamens; they thus frequently come in contact in the first 
instance with a stigma, and may thus cause cross-fertilisation. 
On the other hand, they often come in contact first with some 
of the anthers and thus occasion self-fertilisation. Later on, the 
petals and stamens draw together towards the axis of the flower, 
thus bringing anthers and stigmas in contact with one another, 
and insuring self-fertilisation. 
Although the flowers have only pollen to offer, they attract 
a good many honey-seeking insects, which fly away again after a 
vain search for honey, and after sometimes even boring into the 
tissue at the base of the flower. I have noticed the following — 
insects on the flowers of H. perforatum :— 
A. Hymenoptera—(a) Apidae: (1) Bombus agrorum, F. 9, ¢p.; (2) B. 
terrestris, L. %, cp. ; (3) Saropoda bimaculata, Pz. ?, s. ; (4) Andrena dorsata, 
K.9,cp.; (5) A. coitana, K. 9, cp. ; (6) Nomada lineola, Pz. 2,8. ; (7) N. 
lateralis, Pz. 9,8; (8) Prosopis armillata, Nyl., fip.; (b) Tenthredinide : 
(9) Tenthredo sp., vainly seeking honey. B. Diptera—(a) Bombylide: 
(10) Argyromeeba sinuata, Fallen, vainly seeking honey ; (11) Bombylius 
canescens, Mik., s.; (b) Empide: (12) Empis livida, L., s., the two last 
obviously bored into the base of the flowers; (c¢) Syrphidw: (13) Eristalis 
nemorum, L, ; (14) E. arbustorum, L. ; (15) E. tenax, L. ; (16) E. sepuleralis, 
L. ; (17) Syrphus balteatus, Deg. ; (18) S. ribesii, L., all six species very ab. ; 
(19) Helophilus pendulus, L.; (20) H. trivittatus, F.; (21) Melanostoma — 
mellina, L. ; (22) Melithreptus scriptus, L. ; (23) M. pictus, Mgn. ; (24) Ascia 
podagrica, L., all these Syrphide were diligently collecting pollen. C. Lepi- 
doptera—Rhopalocera : (25) Hesperia silvanus, Esp. ; (26) Satyrus Janira, L. 
both thrust their proboscides to the base of the flower, but were obviously 
groping about for honey and unable to pierce the necfariferous tissue. D, Co- 
leoptera—Chrysomelide : (27) Cryptocephalus sericeus, L., devouring both 
stamens and pollen. See also No. 590, 11. 
Hypericum tetrapterum, L., is visited by pollen-collecting bees 
and pollen-feeding flies (590, I1.). 
Hypericum hirsutum, L.—The structure of the flowers for the most — 
part resembles that of H. perforatum, but they are smaller and 
have far fewer stamens, only seven to nine in each bundle. The 
plants bear fewer flowers, and stand more isolated, which greatly 
restricts the number of insect-visitors; in fact, I have never 
succeeded in observing H. hirsutwm visited by any insect. The 
bundles of stamens, on account of the small number they contain, 
are separated by wider intervals, in which the styles pass outwards 
