MILKWEED FAMILY ASCLEPIADACEAE 
The Milkweed family consists of about 2,000 widely distrib- 
uted species, most of which are found in the tropics and 
warmer temperate regions. 
As a whole, the family is characterized by paired leaves, 
copious milky juice or latex, and curiously shaped flowers. It 
furnishes some minor drugs, one or two notorious weeds such 
as the Common Milkweed and the Anglepod, and in young 
shoots of the former possible asparaguslike food for human 
beings. The latex contains the hydrocarbons that form rubber, 
which has been produced experimentally from some species. 
Some of the flowers are beautiful and delightfully fragrant, 
and others are ill smelling, but all have practically the same 
highly specialized form for insect pollination. The formation, 
however, is not to insure self-pollination, as stigma and anthers 
do not ripen together, but is to compel visiting insects to gather 
pollen in the act of sipping nectar from the flower. From the 
base of the corolla grows a corollalike structure called the 
crown. The 5 lobes of the crown are united at the base, usually 
into a short column or collar whose height varies with the spe- 
cies, and bear at varying heights along their inner surface 
spurs which may or may not be included in the crown. The 
lobes are usually called hoods and the spurs are referred to as 
horns. The whole structure surrounds the stamens and forces 
the anthers to touch in a circle around the pistil. In most cases 
the filaments are united into a column. Sepals and petals are 
reflexed in full bloom. 
Insert a pin into one of the slits in the crown, with the 
point inward toward the anthers. Pull upward and you will 
find 2 pollen masses adhering to the pin. Now the bee, when it 
comes in search of nectar, alights on the adequate surface of 
the crown. It is highly probable that its foot will slip into one of 
these crevices, engage the pollen masses much as the pin did, 
and pull them out as the foot is withdrawn. The insect flies to 
another flower where it may come in contact with the stigmatic 
surface and deposit some of the pollen; often, however, its foot 
is caught too tightly and it dies. 
The fruits are follicles, many of whose seeds are copiously 
provided with silky hairs, collectively called a coma, which 
aid in distribution. These comae are dyed and used extensively 
for ornamentation. 
KEY TO GENERA 
Bercee-itcen in umbels...) 2: 20) 8, Cee Acerates p. 247 
Flowers not green in umbels... 9 Asclepias p. 243 
