part ut.) | THE MECHANISMS OF FLOWERS. _ 433 
Linaria Cymbalaria, Mill. is visited chiefly by bees (590, tt.). 
Cleistogamic flowers occur in Linaria according to Michalet (524) 
and Kuhn (399). 
321. ANTIRRHINUM MAJUS, L.—This plant differs from Zinaria 
vulgaris (1) in the much greater size of its flowers, into which our 
largest humble-bees can enter bodily, (2) by its more firmly closed 
entrance, which excludes the smaller bees, (3) in its nectaries and 
honey receptacles. 
The honey is secreted, as Sprengel suggested, by the smooth, 
green, fleshy base of the ovary, whose upper part is paler in colour 
and covered with fine hairs; but it does not flow, as Sprengel 
thought, down into the short spur—which is hairy within, and for 
that reason unfitted to be a honey-receptacle, but it remains ad- 
herent to the nectary and to the base of the anterior stamens. The 
short wide spur permits the insect’s proboscis to reach the honey 
from below ; above and in front it is protected by a thick fringe of 
stiff, knobbed hairs on the angles of the anterior stamens. - 
The flowers are fertilised chiefly by humble-bees, of which I 
have observed the following species: (1) Bombus hortorum, L.; 
(2) B. terrestris, L.; (3) B. agrorum, F.; (4) B. silvarum, L.; 
(5) B. lapidarius, L. The females and workers, and in late summer 
the males also, creep bodily into the flower, and creep out backwards 
dusted on their backs with pollen. From time to time they brush 
off the adhering pollen from their thorax with the tarsal brushes 
of the fore and midlegs, and from the abdomen with the tarsal brushes 
of the hindlegs. Not only the females and workers, but the males 
also, perform this action, which seems, therefore, to be done more for 
cleanliness than to collect the pollen, though the females and workers 
naturally make use of it, placing it in the pollen-baskets on their 
hindlegs. I have also seen Anthidium manicatum, L. 2, Megachile 
| fasciata, Sm. 3, and Osmia rufa, L. 2, creep into the flower and 
emerge with their backs covered over with pollen. Smaller bees 
only exceptionally creep into still fresh flowers, and are useless to 
the plant: I have only once seen Megachile centuncularis, L. ?, 
succeed in entering; on the other hand I have repeatedly seen 
- small species of Halictus (H. zonulus,Sm. °, H. morio, F. 2, H. 
Smeathmanellus, K. 3) flying from flower to flower until they 
reached an old flower, which in withering had opened slightly and 
permitted them to enter. This showed clearly how far the fast 
closure of the mouth is useful to the plant; if the small bees 
could enter from the first, they would use up much of the honey, 
FF 
