This section is from the book "Nature's Garden", by Neltje Blanchan. Also available from Amazon: Nature's Garden; An Aid To Knowledge Of Our Wild Flowers And Their Insect Visitors.
Flowers - Funnel form, wide-spread, 2 to 3 in. long, pure svhite or pinkish purple inside the throat; the peduncles 1 to 5 flowered. Stem: Trailing over the ground or weakly twining, 2 to 12 ft. long. Leaves: Heart, fiddle, or halbert shaped (rarely 3-lobed), on slender petioles. Root: Enormous, fleshy.
Pre/erred Habitat - Dry soil, sandy or gravelly fields or hills.
Flowering Season - May - September.
Distribution - Ontario, Michigan, and Texas, east to the Atlantic Ocean.
No one need be told that this flaring, trumpet-shaped flower is next of kin to the morning-glory that clambers over the trellises of countless kitchen porches, and escapes back to Nature's garden whenever it can. When the ancestors of these blossoms welded their five petals into a solid deep bell, which still shows on its edges the trace of five once separate parts, they did much to protect their precious contents from rain; but some additional protection was surely needed against the little interlopers not adapted to fertilize the flower, which could so easily crawl down its tube. Doubtless the hairs on the base of the filaments, between which certain bumblebees and other long-tongued benefactors can easily penetrate to suck the nectar secreted in a fleshy disk below, act as a stockade to little would-be pilferers. The color in the throat serves as a pathfinder to the deep-hidden sweets. How pleasant the way is made for such insects as a flower must needs encourage! For these the perennial wild potato vine keeps open house far later in the day than its annual relatives. Professor Robertson says it is dependent mainly upon two bees, Entechnia taurea and Xenoglossa ipomoeae, the latter its namesake.
One has to dig deep to find the huge, fleshy, potato-like root from which the vine derived its name of man-of-the-earth. Such a storehouse of juices is surely necessary in the dry soil where the wild potato lives.
Happily, the common Morning-glory (/. purpurea) - the Convolvulus major of seedsmen's catalogues - has so commonly escaped from cultivation in the eastern half of the United States and Canada as now to deserve counting among our wild flowers, albeit South America is its true home. Surely no description of this commonest of all garden climbers is needed; every one has an opportunity to watch how the bees cross-fertilize it.
The vine has a special interest because of Darwin's illuminating experiments upon it when he planted six self-fertilized seeds and six seeds fertilized with the pollen brought from flowers on a different vine, on opposite sides of the same pot. Vines produced by the former reached an average height of five feet four inches, whereas the cross-pollenized seed sent its stems up two feet higher, and produced very many more flowers. If so marked a benefit from imported pollen may be observed in a single generation, is it any wonder that ambitious plants employ every sort of ingenious device to compel insects to bring them pollen from distant flowers of the same species? How punctually the Moon-flower (/. grandiflora), next of kin to the morning-glory, opens its immense, pure white, sweet-scented flowers at night to attract night-flying moths, because their long tongues, which only can drain the nectar, may not be withdrawn until they are dusted with vitalizing powder for export to some waiting sister.