CONVOLVULACE^ 555 



tube of the corolla and alternate with its lobes; all are 

 anther-bearing. The filaments are filiform, or dilated at the 

 base, and equal or unequal. The anthers are two-celled, and 

 longitudinally dehiscent. The ovary is superior and usually 

 has two cells (rarely three cells), each of which bears two 

 ovules. In some instances, the ovary is falsely divided into 

 four to six cells, each with a single ovule. 

 Fruit.^ — The fruit is a capsule; its seeds are endospermous. 



Key to Important Genera 



Stigmas capitate (knob-like). 



Stamens and style exserted, Quamoclit. 



Stamens and style included, Ipomosa. 

 Stigmas two, filiform or oblong, Convolvulus. 



IPOMCEA BATATAS (Sweet Potato) 



Roots and Stems. — The sweet potato is a sinistrorse-twin- 

 ing, trailing, perennial herb with very much thickened roots. 

 The "sweet potato" itself is often designated as a "root 

 tuber." The fleshy roots have stored within them large 

 quantities of starch. They should not be confused with the 

 tubers of the Irish potato. Sweet potato "tubers" are roots, 

 while Irish potato "tubers" are stems. 



Propagation. — In the propagation of sweet potatoes, these 

 fleshy roots are cut lengthwise, and the cut surface of each 

 piece is laid against moist earth until it produces sprouts. 

 Then the piece is further cut up and each portion replanted. 

 It is necessary to leave a part of the epidermis in order that 

 adventitious buds will develop. Sweet potatoes are fre- 

 quently propagated by vine cuttings. 



Leaves.— These are alternate, heart-shaped, petiolate, 

 dark green, and glossy. 



Inflorescence and Flowers.— The large, purple, con- 

 spicuous flowers are axillary, solitary or cymose. The 



