part mt.] © .THE MECHANISMS OF FLOWERS. 437 
Vandellia, L., has cleistogamic flowers (399). 
323. DIGITALITIS PURPUREA, L.—Honey is secreted by an 
annular ridge surrounding the base of the ovary (a, 1, 2, Fig. 147). 
This ridge is not ‘covered thickly with short hairs’ as Sprengel 
described it, but is perfectly smooth ; the ovary only becomes hairy 
above the ridge. 
The anthers and stigma lie pointing downwards near the upper 
wall of the corolla. The longer stamens are ripe before the shorter 
ones, and these before the stigma, The dimensions of the flower 
Fic. 147.— Digitalis purpurea, L. 
1.—Young flower after removal of the right half of the calyx and corolla. The taller anthers - 
eS he on the point of dehiscing. This figure should be turned round horizontally in the direction of 
e arrow. 
2.—Tip of style of the same flower, enlarged. 
3.—A-somewhat older flower. ‘The taller anthers are now empty, the shorter pair are dehiscing 
and ate covered with pollen. Viewed from below, after removal of the lower half of the calyx and 
corolla, 
4.—Tip of style of the same flower. 
5.—Empty anthers and stigma of an old flower, from below. 
——— x 
suggest that it is adapted for humble-bees, for no other native 
insects are large enough to touch the stigma and anthers with 
their backs when creeping into the tube; and, as a matter of fact, 
humble-bees are the only fertilisers of the Foxglove. Sprengel, on 
_ the title-page of his work, represents B. terrestris, ? , creeping into 
__ this flower. When bees frequent the plant abundantly, all the four 
_ anthers are emptied of their pollen before the stigmatic lobes 
i. (, 1, Fig. 147) separate. In absence of humble-bees, the anthers 
remain covered with pollen until the stigmatic lobes have 
_ spread apart; and then when the corolla falls off this pollen is 
