Robertson — Flowers and Insects — Labiate. 109 
blooming from May 17 to June 18. The plants are often 
collected in conspicuous patches. The stem rises 3 to 6 dm. 
and bears a large terminal head of pale purplish flowers. 
The corolla is about 40 mm. in length and is divided for 
about half its length into strongly divergent lips. The upper 
lip is linear and measures about 20 mm. in length. Below, 
it is folded over the style and filaments; at tip it is provided 
with a beard the significance of which will be explained 
below. The lower lipis oblong and deeply channelledabove — 
the groove forming a guide for the proboscides of the 
visitors. This lip is ornamented with purplish dots. The 
two anthers are situated under the tip of the upper lip, but are 
very feebly sheltered by it. The stigma is several mm. in 
advance of the anthers; its upper lobe is nearly aborted, the 
lower is long and curled downwards when receptive. 
The flowers are proterandrous, but if the anthers retain 
some of their pollen until the stigma is receptive, spontane- 
ous self-pollination is impossible on account of the wide sep- 
aration of anthers and stigma. The flowers may be pollinated 
by insects with pollen from flowers of the same or of distinct 
plants. 
The upper lip is slightly arched over the lower one; then 
the anthers, when dehiscent, and the stigma in turn when re- 
ceptive, bend a little downwards so as to be more likely to 
touch the back of an insect settling upon the lower lip, but 
the lips still remain so strongly divergent that a consideration 
of the floral mechanism and the varying conditions in the re- 
lations of the visitors becomes exceedingly interesting. 
At its origin, the upper lip is nearly perpendicular to the 
axis of the lower. Their tips are about 20 mm. or more apart. 
The dehiscent anthers and receptive stigma stand about 10 mm. 
above the highest part of the lateral edge of the lower lip. 
It is evident that only the largest insects are likely to touch 
these organs while resting upon the lower lip. The tube 
measures about 18 mm., its upper part being wide enough to 
admit the head of a bumble-bee for about 5 mm. This also 
indicates an adaptation to large insects with long tongues. The 
early blooming of the flower is also significant, for at this 
time the female bumble-bees, which are much larger than the 
