88 
Bulletin Wisconsin Natural History Society. [Vol. 5, No. 2. 
Mitella diphylla L. ]Mitrewort. 
The small, white, cup-shaped flowers, blooming from about 
]\Iay 5 to June 15, are adapted to small-sized insects. Syrphid- 
flies and short-tongued bees are the principal visitors, and the 
smallest among these belonging to the fly-genus Paragus, and the 
bee-genus Halictus are the most* frequent ones, as far as the 
number of individuals is concerned. The flowers are arranged in 
a terminal raceme on a scape that attains a length of 30 to 40 cm. 
At its entrance the flower is 2 mm. wide, its depth is the same, 
and the nectar-drops on the lower portion of the calyx-tube are 
easily reached by insects with very short mouth-parts. The small, 
triangular calyx-lobes are erect, while the much longer white 
petals, with their fringed appearance, are spread out laterally or 
reflexed, as in the older flower. There are 10 stamens, all of 
them arising at the same level from the wall of the calyx and con- 
verging towards the middle, thereby forming with their anthers 
a small circle below the mouth of the flower. The very short 
styles, with their stigmas, are situated somewhat below the anthers. 
In the opening flower the anthers are all nearer to the calxy-tube 
but as those of the 5 stamens that alternate with the petals begin 
to open, they move towards the middle, and later on the 5 
remaining stamens undertake the same movements. Proterandry 
is present, but of short duration, since the stigmas reach maturity 
very soon after the first anthers have burst open. In view of the 
vertical position of the flower, spontaneous self-pollination by the 
falling of pollen can hardly be expected, at least not in the young 
flowers. But the styles increase in length and place the stigmas 
beneath the anthers, and in the older flower this kind of pollina- 
tion may take place if pollination through insects has not been 
accomplished previously. The latter are mostly present to such 
an extent as to insure either cross or self-pollination. Pollen is 
transported by the mouth-parts of the visitors. When in search 
of nectar an insect has to insert its proboscis between the stigmas 
and the introrse anthers, whereby some of the pollen adheres to 
the sides of the proboscis and in this way may be brought in con- 
