58 FAMILIES OF FLOWERING PLANTS. 
is a 3 angled capsule, shown in the accompanying illustration. of our 
common wild yam (See Fig. 49). In other genera, as Tamus, the 
fruit is a berry.. : 
The large fleshy rootstocks of some tropical species fhrnish the 
yams of commerce. Many have the peculiar habit of producing 
fleshy tubers, often called ‘‘air potatoes’’ in the axils of their upper 
leaves; these tubers sometimes attain considerable size. 
Fic. 50.—Dwarf crested iris (Jris cristata). Original. 
Family Iridaceae. Iris Family. A group of considerable size, 
containing about 60 genera and over 1000 species, widely distributed 
over the warmer parts of the globe. ‘They shun the cold and in our 
temperate climate we have besides /ris itself only three small genera. 
On the other hand a great number of genera and species flourish in 
South Africa, and many of them are endemic there. This results in 
the common use among horticulturists of the term ‘‘Cape bulbs’’ to 
designate such plants as Jaa, Spararis and Freesia, all well known. 
as pot, bulbs. 
