314 Field, Forest, and Wayside Flowers 
seldom receives and nourishes all comers. In one 
peculiarity of structure the milkweeds are like the 
orchids, that royal family of plants, for many or- 
chids also send their pollen abroad massed into 
two clusters, which are united by a disk. But each 
orchid has its own very select and small circle of 
guests, and some among them endeavor to please 
one butterfly or moth friend, him and him alone. 
They are, in evolutionary language, ‘‘highly spe- 
cialized.’”’ 
On the other hand, a flower which keeps open 
house to all comers is generally primitive in color 
and structure. Such blossoms are apt to be yel- 
low or white, with flat, open corollas, and without 
spurs, honey-jars, or covering to protect the pollen. 
So the milkweed is something of a problem to the 
evolutionary botanist. 
And there is another puzzle for him in the in- 
adequacy of Nature’s very elaborate contrivances 
to ensure the fertilization of the milkweed. Flowers 
far simpler in structure and far less attractive to 
insects bring a larger proportionate number of fruits 
to perfection. 
The great blossom-clusters which crown the milk- 
weed in July and August are made up of from 
twenty-five to fifty flowers. But in September the 
