DICOTYLEDONS: SYMPETALUE 313 
should be recognized as Sympetale, are honeysuckle, elder, 
lobelia, bluebell, primrose, morning-glory, lilac, milkweed, 
gentian, phlox, mullein, snapdragon, and verbena. Some 
additional prominently useful plants are as follows: 
Sweet potato belongs to the same genus (/pomea) as the 
morning-glory, having long trailing stems and clusters of 
the well-known large oblong or elongated roots. It is not 
known whether it is native to the East Indies or America, 
but it is extensively cultivated in all warm countries. In 
the United States the cultivation of the sweet potato as a 
commercial crop is confined almost exclusively to the South- 
ern States, but important areas are found also in New Jer- 
sey, Ohio, Indiana, and 
Illinois. The varieties 
called yams in the South 
are all sweet potatoes, 
and the name really be- 
longs to a very different 
plant. 
Olive.—The olive-tree 
has been known and cul- 
tivated from the most 
ancient times, and has 
entered largely into the 
life and customs of Med- 
iterranean peoples (Fig. 
300). It is thought to 
be a native of southern 
Europe and Asia Minor, 
and thrives best in dry 
climates such as those of 
; é : Fic. 300.—Flowering branch of olive. 
Syria and Assyria. It is efter Tat now:, 
cultivated also at the 
Cape of Good Hope, in Australia, and in California. It 
is a very long-lived tree, a thousand years having been 
