ARROWROOT. 



343 



STAECH-PRODUCING PLANTS. 



Starcli is the chemical and common name, in some instances, for 

 the fecula or amylaceous matter washed out from different parts of 

 several plants, such as the seeds, roots, and cellular tissue of the 

 stems. It is one of the most abundantly diffused of all proximate 

 vegetable principles. 



Some kinds of starch are prepared for application in the arts, and 

 by the laundress for stiffening linen ; others are more powdery and are 

 used for food, such as the arrowroots and corn flours ; others again are 

 granulated like the sagos and tapiocas. 



The colour of starch is usually pure white. In some cases a tinge 

 of blue can also be seen, as in some wheat starch, while the starch 

 from the potato has a slightly yellowish cast. The fineness of the 

 starch powder depends on the size of the individual grains, except 

 where the grains are artificially agglomerated, as in sago and tapioca ; 

 the former is in small, round, white or brownish grains, while tapioca 

 is in larger, irregular, white fragments. The individual starch grains 

 vary much in size, though they are pretty constant in any given 

 species. Oat, rice, and rye starches represent the smallest grains, 

 while those of maize starch are much larger. The medium size is 

 found in the grains of wheat and arrowroot starch. The largest grains 

 are found in potato and Canna starch. In the last two the unaided 

 eye can distinguish the largest individual grains, but in nearly all 

 others they can be seen only under the microscope. The specific 

 gravity is more than that of water, though it varies much with the 

 state of dryness of the starch. Its average is given by Wiesner at 

 1 • 5. It, however, varies with the different species of starch. The 

 grains contain considerable water— as high as 80 per cent, when fresh, 

 reduced sometimes to 7 per cent, when air dry. 



Under the microscope the starch grains present the form of minute 

 grains of a form and structure characteristic for each species. 



They are for the most part bounded by curved surfaces — spherical, 

 elliptical, egg-shaped, bent-shaped, &c. — but sometimes they have flat 

 surfaces as well. They usually contain a dark spot, line, or cross 

 within, which is sometimes central, sometimes eccentric. This spot 

 is called the nucleus, and is generally small and round in starch found 

 in fresh tissues, slit or cross-shaped in grains which have been dried.* 



Arrowroot. — The demand for colonial arrowroots has not pro- 

 gressed very rapidly, owing, probably, to the imitation potato starch, 

 and the corn and rice flours or starches so largely sold. 



In 1860 arrowroot to the value of 42,404/. was imported into the 

 United Kingdom, in 1870 this had dropped to 33,068Z., but in 1875 

 recovered to 56,143Z. In 1876 the imports into London were larger, 

 amounting to 16,673 casks and 9102 boxes and tins. 



* Professor Harrington, in ' Ameriotin Journal of Pharmacy.' 



