MICKOSCOPY OF THE COMMON STARCHES. 67 



special purposes, and are rather liable to sophistication. 

 The characters of the group vary widely, and we can only 

 consider one common example. Bermuda arrowroot has 

 a starch which in its flattened ovoid shape and the posses- 

 sion of oyster-sheU markings resembles that of the potato. 

 The grains are however smaller, .02-.03 mm., and the 

 hilum, usually at the larger end of the grain, is typically 

 elongated to the form of a slit. The smaller grains are 

 not rounded as in potato-starch, but have the same shape 

 as the larger ones. 



II. Sago and the Cassavas. — ^Tapioca is derived from 

 the root of the bitter or poisonous cassava, the hydro- 

 cyanic acid which it contains being driven off in the pro- 

 cess of manufacture. The sweet cassava, in which this 

 substance is not present, yields a similar starch which 

 has recently been introduced into the trade for certain 

 sizing processes to which it is supposed to be specially 

 adapted. Tapioca starch-grains are very smoothly cir- 

 cular and often show a truncated end. The hilum is 

 central and slit-like. The size is .01-.02 mm. (Fig. 28 (4)). 



The grains of sago-starch have a similar hilum, and 

 occasionally show truncated ends. They are larger than 

 those of tapioca (.02-.05 mm.), and phenomenally irregu- 

 lar, the roughly ellipsoidal form being generally distorted. 



REFERENCES. 



Galt, H. The Microscopy of the. more commonly occurring 



Starches. London, igoo. 

 Leach, A. E. Food Inspection and Analysis. New York, 1904. 

 Maurizio, a. Getreide, Mehl und Brot. Berlin, 1903. 

 ScHiMPER, A. F. W. Anleitung zur mikroskopischen Untersuch- 



