108 THE FERTILISATION OF FLOWERS. [PART III. 
part of its proboscis or head. As we have scen in other cases, 
this must regularly lead to cross-fertilisation if the insect thrusts 
its head only once into the flower, but may equally well produce 
self-fertilisation if it does so more than once. In absence of 
insects self-fertilisation is always accomplished by means of the 
longer stamens. 
On April 27 and 28, 1872, I and my son Hermann saw the 
following insects visit a luxuriant patch of Teesdalia in sunny 
weather :— | 
A. Hymenoptera—A pide : (1) Sphecodes ephippia, L., sucking on thirteen 
inflorescences successively. B, Coleoptera—(a) Chrysomelide: (2) Haltica 
nemorum, L., three specimens, apparently sucking ; (8) Plectroscelis dentipes, 
E. H., one specimen, do. ; (4) Cassida nebulosa, L., two specimens flew on to 
the inflorescence without making use of the flowers; (b) Curculionide: (5) 
Ceutorhynchus pumilio, Gylh., two specimens, s. ; (¢) Elateride : (6) Limonius 
parvulus, Pz. ; (d) Hydrophilide : (7) Cercyon anale, Pk. (these last two beetles 
also settled on the flowers, but I could not see that they made use of them in any 
way). C. Diptera—(a) Syrphide : (8) Melithreptus sp. ; (9) Ascia podagrica, 
F., both fp. ; (6) Muscide: (10) Sepsis putris, L., ab., s. Also many minute 
Muscidz and gnats, 1 to 4 mm. long. 
Biscutella levigata, L., is homogamous. I have found it 
visited by thirty-six species of insects, mostly Diptera (609). 
Hesperis tristis, L.—This plant, by elongation and close approxi- 
mation of the sepals and the claws of the petals, excludes all 
insects except Lepidoptera from its honey. By the time of ex- 
panding and emitting its perfume it has become adapted for 
cross-fertilisation by crepuscular and nocturnal forms (570, vol. xii.). 
34. HESPERIS MATRONALIS, L.—Honey is secreted by two 
very large, green, fleshy glands surrounding the base of the shorter 
stamens, and especially developed on their inner sides; it collects 
on each side of the flower between the pistil and the bases of 
the three stamens of that side. 
The taller anthers stand at the entrance of the flower, and only 
project beyond it when they have withered. ‘The shorter stand a 
little deeper within the flower, and when they dehisce their tips 
closely surround the stigma, which is afterwards protruded beyond 
the flower by the lengthening of the pistil. All the anthers 
dehisce inwards, and cover the stigma with pollen. If insect- 
visits take place at the proper time, cross-fertilisation is also 
effected: regularly by the honey-seeking species, for they touch 
