It6 ELEMENTARY AGRICULTURAL CHEMISTRY 



ihe Sweet Potato (Ipoinoea batatas or Batata edalis). — Thia 

 ig a convolvulus-like plant, usually with purple flowers, pro- 

 ducing tubers on its roots, sometimes of great size, up to 121b. 

 or more in weight. It is essentially a tropical or sub-tropical 

 crop, and does best in light, friable soils rich in organic matter. 

 It is propagated by cuttings, and once established on land will 

 yield several crops in succession. A fair crop is four or five 

 tons to the acre. 



The tubers are used in the same way as the ordinary 

 potatoes, but are sweeter and more nutritious. The leaves 

 and stems are eaten greedily by horses, cattle, and sheep, 

 but it has recently been shown that they sometimes contain 

 a glucoside which decomposes and yields hydrocyanic acid 

 (prussic acid). Amounts varying from 0014 to 0019 per 

 cent, of the green material were found. Numerous cases of 

 death in pigs fed on sweet potato vines were observed in 

 Queensland in 1905. 



Average Composition of Sweet Potatoes and their Vines. 



Water . 

 Ash . 

 Crude fibre . 

 Carbohydrates 

 Protein 

 Fat . 



Tubers. 



71-1 

 1-0 

 1-3 



247 

 1-5 

 0-4 



100-0 



Vines. 



41-6 



5-8 



13-6 



29-3 



7-6 



2-1 



1000 



The Carrot {Daucus carota) and the Parsnip {Pastinaca 

 sativa) are also sometimes grown as farm crops. The roots are 

 used as vegetables, and as an excellent food for horses and cattle. 

 Also belonging to this family of Umbelli ferae are Celery {Apium 

 graveolens)y Parsley {Petroselinum sativum)^ and Caraway 

 {Garum carui). 



