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 Tamvs, 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. 



Fjg. 50.— Dwarf crested iris (Irm cristata). OriKinal. 



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. The}' shun the cold and in our 

 temperate climate we have besides Iris 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 Txia, Sjxiraxis and Freesla, all well known 

 as pot bulbs. 



