490 THE FERTILISATION OF FLOWERS. [PART III. 
In the large-flowered form the tube is 7 to 8 mm. long; the 
longer stamens divide above into two very divergent branches, of 
which one, slightly shorter than the other, is turned towards the 
middle line of the flower and bears the two anther-lobes ; the other 
branch is turned outwards, and its pointed end rests upon the con- 
cave surface of the upper lip, and insures the anthers (which dehisce 
inferiorly) being in the position on either side of the stigmas where 
they are most certain to be touched by a bee-visitor. Dr. Ogle 
explains these processes of the filaments in a similar way (632). 
The shorter stamens also divide into two branches (Fig. 165), 
which are much shorter, but serve the same purpose. 
Owing to the position of the anthers, the dorsal surface of the 
bee comes first in contact with the stigmatic papille of the inferior 
stigma, and is afterwards dusted with new pollen. In the event 
of insect-visits cross-fertilisation is thus fully insured. I have 
never observed spontaneous self-fertilisation in absence of insects 
in any of the plants which I have kept in my room. According 
to Axell, however, this plant produces seed by self-fertilisation 
when insects are excluded (17). 
Visitors: A, Hymenoptera—Apide: (1) Apis mellifica, L. $ (6); (2) 
Bombus silvarum, L. § (10) ; (3) B. lapidarius, L. ¢ (8—10) ; (4) B. pratorum, 
L. % (8); (5) B. terrestris, L. § (7—8) ; (6) Megachile Willughbiella, K. ¢; 
(7) Anthophora furcata, Pz. ¢ (11—12), all sucking normally ; the females 
sometimes have pollen in their baskets; (8) Cilissa hemarrhoidalis, Pz. ¢, 
tried in vain to suck the large-flowered form,—it dusted itself with pollen on 
the large flowers, and so in passing to the small ones, which it can suck easily, it 
effected cross-fertilisation. B. Lepidoptera—Rhopalocera : (9) Lyceena argiolus, 
L. ; (10) Hesperia silvanus, Esp. ; (11) Melitzea Athalia, Esp., all three sucking ; 
their thin tongues enter the flower without touching the essential organs. See 
also No. 590, 111., for a further list of visitorsin Low Germany. A list of Alpine 
visitors (one fly, five humble-bees, ten Lepidoptera) is given in No. 609. 
Prunella grandiflora, Jacq.—The four anthers lie parallel with 
one another on the same level, and the two outer stamens are bent 
downwards by a special mechanism as soon as a bee thrusts its 
proboscis down into the flower. The unusually wide corolla-tube 
- shows two shallow invaginations on each side. One pair are placed 
about the middle of the corolla, in its anterior (inferior) half, and 
are prolonged directly into the outer stamens which then pass 
backwards and course upwards close beneath the upper lip. At 
one point they are grasped by the posterior invaginations, and are 
thus divided into two parts, and form levers of which the upper 
arm is four times as long as the lower, the fulcrum being furnished 
by the posterior invaginations of the corolla. The bee, in inserting 
