FAMILIES OF FLOWERING PLANTS 223 
Several very poisonous trees of the Apocynaceae are of interest as 
being “ ordeal trees.” The most familiar of these is the tanghin, Tan- 
ghima venenifera, confined to Madagascar. The natives use the seeds 
in the trials of evil-doers, forcing each culprit to swallow a portion. In 
case the seed is retained in the stomach it proves immediately fatal, and 
guilt is then considered established. If on the other hand it is vomited, 
Fic. 193. The Swamp Milkweed (Asclepias incarnaia). After Britton 
and Brown, Ill. Fl., Northeast, U. S. 
recovery usually ensues, and the prisoner is released as innocent. In 
Polynesia Cerbera is used in a similar manner. 
Family Asclepiadaceae. Milkweed Family. Contains about 220 
genera and 1,900 species, of wide distribution. They are herbs, vines 
or shrubs, with milky juice, and flowers borne usually in umbels. The 
corolla and calyx are 5-parted ; between the corolla and stamens is a 
5-parted body, known as a crown or corona. The pollen is coherent in 
masses, as in the orchids, and exhibits many interesting adaptations to 
cross-fertilization through insect agency. The ovary consists of two 
carpels, which become follicles in fruit; the seeds are usually appen- 
daged with a long tuft of hair or coma. The milkweeds proper (As- 
clepias) are among our most showy wild flowers; the different species 
exhibit orange, yellow, pink, purple and white flowers (Figs. 192 and 193). 
In the desert regions of northern Africa there are a number of leafless 
succulent plants belonging to this family; these, with Huphorbias of 
similar habit, replace the cacti of our western plains. The juice is often 
‘poisonous, like that of the dogbanes, but in some cases it possesses val- 
uable emetic and purgative properties. The family is very widely dis- 
tributed, but is particularly abundant in South Africa. , 
