No. 401.] THE FRUITING OF THE BLUE FLAG. 363 
elastically, and the rubbing of an emerging insect only closes 
it the more tightly. 
Although the flowers are slightly protandrous, ripe pollen 
and fresh stigmatic surface may be found in the same flower at 
some period of zstivation. In case insects fail there is no pro- 
vision for self-pollination by withering, as is the case in some 
members of the Iris family; the stigma, lifted away from the 
anther before maturing, remains so permanently. 
I shall now discuss briefly the insects which I have seen to 
enter these flowers, taking them up in the order of their impor- 
tance as agents of pollen distribution. I therefore begin with 
two small bees of closely similar size and habits: C/isodon 
terminalis Cr., Osmia distincta Cr. 
These bees exhibit such perfection of adaptation as was the 
delight of the naturalists of Sprengel's day, and as will ever be 
delightful to observe. They were seen only in warm sunshine, 
during the season of abundant flowers; late and straggling 
flowers seemed to be neglected by them altogether. They 
were not the most numerous nor the most conspicuous visit- 
ors ; but they visited very many flowers in rapid succession, 
securing the transference of the pollen with superior precision. 
Each bee alights squarely at the entrance and without the 
slightest pause speeds down the arched passageway, and does 
not stop until its head is wedged in the bottom, with the pro- 
boscis extended through one of the two holes (see Fig. 1, 5) 
leading to the nectary. A step backward and another momen- 
tary thrust of the proboscis, and away to another flower. That 
it rubs the stigma on entering may be seen by the tilting of 
the style tip; this is readily seen at a distance of several 
meters. Osmia distincta was perhaps a little less swift in its 
passage than the other, and this species alone was seen occa- 
sionally stopping on the way out from the nectary to scrape 
up some of the pollen fallen beneath its feet. 
Next in order should be mentioned a group of syrphus flies : 
Helophilus letus Loew.; Syrphus torvus O. S.; Eristalis dimi- 
diatus Wied. Of these the first-named was a very common 
visitor. Of the other two I saw but a single specimen of each 
on Iris flowers, although the last-named was abundant on flowers 
