IPOMCEA. 187 



turning is always against the sun — from right to left, con- 

 trary to the twisting of its corolla buds.* 



The ^oot has no such aspiration. Growing downward 

 from the first moment of its breaking through the seed-coats, 

 it persistently avoids the air and light, seeking the dark, 

 damp depths of the soil. Its innumerable fibers are so many 

 mouths absorbing water and earthy matters, which ascend 

 and mix with the air and gases absorbed by the leaves. 

 Chemical action is induced by the rays of the Sun, trans- 

 forming all into nourishing sap for the life and growth of 

 every part of the plant. 



The Name. — By the latest authorities {Bentliam tO 

 Hool'er^s Genera), the Morning Glory is called Ipomoea pur- 

 purea. But it has many synonyms. In 1750, Linnaeus first 

 named it Convolvulus purpiireus. In 1790, Lamark trans- 

 ferred it to the genus Ipomcea. In 1810, Choisy separated 

 it, together with all other 3-carpelled species, from Ipomoea 

 to his new genus, Pharbitis. Ipomoea is from ips, Greek for 

 Bindweed, omopos, like. 



Classification. — The order Coxyolvulace^ — the 



Bindweeds — represented by the Morning Glory, is limited 



as follows : 



Herbs trailing or cUmbing, with alternate leaves. 



Flowers regular, 5-parted, perfect. 



Calyx of 5 sepals imbricated in aestivation. 



Corolla of 5 united petals, supervolute in aestivation. 



Stamens 5, unequal, adhering to the corolla tube. 



Ovary and capsule 3 or 3-carpelled, 2-4-celled. 



Seeds with large embryo and thin albumen. 



The Bindweeds number 32 genera and 800 species, chiefly inhuD 

 iting the warm regions of the globe. 



The Sweet Potato is Batatas edulis, a vine resembling the Morning 



* Tt seems to he a common law among twininp vines that each species should twine 

 invariably in one direction— some (as the Hop) always with the Sun, others (as Moru- 

 ing Glory) against the Sun. 



