12 STARCHES. 



(7) Potato Starch. 



Potato starch (Fig. 7) is obtained from the tubers of Solanum tube- 

 rosum, Linn. It is composed of grains of variable size, some being so 

 large as to be visible to the naked eye. Typical grains of this starch 

 are flattened, and have an oval, ovate, ellipsoidal or conchoidal out 

 line. The hilum is punctiform, eccentric, and generally situated in 

 the narrow end of the grain ; it is surrounded by numerous distinct 

 concentric striations, some few of which are much more conspicu- 

 ous than the others. In addition to these typical grains there are 

 a few others, smaller in size and rounded in outline, or rounded on 

 one side and flattened on the other, these are sometimes attached 

 by their flat sides in twos or threes. 



The largest grains vary in length from 75/x to 110/t, those of 

 medium size from 45/* to 65yu, and the smaller ones from 15^ to 

 25/*. 



(8) Maranta Starch. 



Maranta starch (Fig. 8) is obtained from the rhizomes of 

 Maranta arundinacea, Linn., and other species of Maranta. It is 

 commonly known in commerce as " arrowroot," a term, however, 

 which is also applied to the starches of other and widely different 

 plants. 



The different varieties of arrowroot are distinguished by their 

 geographical sources. Maranta starch is known as Bermuda, 

 St. Vincent, West Indian or Nabal arrowroot, according to the 

 country in which it is prepared. 



The grains of the Maranta starch are simple and rather large. 

 They are irregular in shape, being rounded, ovoid, pear-shaped or 

 sometimes almost triangular ; the smallest ones are nearly spherical 

 The largest bear numerous fine concentric striations, and a con- 

 spicuous rounded, linear or stellate, eccentric hilum. In some 

 varieties of arrowroot (Natal) the rounded hilum predominates, in 

 others (St. Vincent), the linear or stellate ; it often resembles the 

 wings of a poised bird. They average about 30^ to 40^ in length, 

 but may attain to 45/x, 60yu, or even 75/i, as, for instance, in Ber- 

 muda arrowroot ; the smaller grains vary from 7/x, to 15/w. 



