HAWAIIAN TEEE FEKST AS A SOURCE OF STARCH 



11 



(2) Men (Cibotium sp.). (PI. V, fig. 2.) 



Size, 0.01 to 0.05 millimeter (long axis) ; shape, usually elongated disk 

 in the large sizes, but round to oval in the small sizes, and a few truncated 

 and kidney-shaped in all sizes; hilum. usually annular, depressed, eccentric; 

 rings, complete, very distinct ; polarizer, distinct cross at hilum. 

 (S i Hapu Iii or Heii (C. menziesii). (PL VI, fig. 1.) 



Size, 0.01 to 0.04 millimeter ; shape, round to oval, occasionally truncated 

 and angular ; hilum, annular, central, depressed ; rings, very pronounced, con- 

 centric, complete ; polarizer, very distinct cross at hilum. 

 (4) Amau (Sadleria cyatheoides) . (PL VI, fig. 2.) 



Core, mostly colloidal dextrins, with starch grains of extremely minute size. 

 The starch can not be separated from the grated mass by sedimentation ; size r 

 0.01 to 0.03 millimeter : shape, round to oval ; hilum, usually central, annular, 

 depressed ; rings, distinct on large granules, and complete ; polarizer, well- 

 marked cross at hilum. 



The illustrations and morphological descriptions show that the 

 four starches possess many of the same characteristics, the chief 

 differences being in size and shape. Considered from the standpoint 

 of the physical characteristics of the starch granules, each of the 

 four species could be used for starch production. As a matter of 

 fact, the starch of Cibotium chamissoi is very much to be preferred 

 to that of the other three species. The starch of both C. menziesii 

 and Meu, in addition to being of small diameter, contains such large 

 quantities of dextrins and other colloidal matter as to make the 

 separation of the starch difficult. The starch of Sadleria cyatheoides 

 is manifestly unsuitable. 



VISCOSITY 



Since the viscosity curve of a starch, when transformed by boiling 

 water into " soluble starch," is useful in showing its general proper- 

 ties, determination was made of the viscosity of tree-fern starch, 

 and likewise of corn and arrowroot starches for purposes of compari- 

 son. The method of procedure was as follows: Varying amounts 

 of starch were weighed into 100 cubic centimeter flasks graduated at 

 80° C. with 10 cubic centimeters of cold water. Boiling water was 

 added with vigorous shaking, and the flasks were made up to the 

 mark at 80° C. with hot water. The flasks were then placed in boil- 

 ing water for one hour without agitation, after which they were 

 quickly cooled to 80° C. with as little agitation as possible, and the 

 viscosity was determined with a Saybolt universal viscosimeter at 

 that temperature. Duplicate determinations by the above arbitrary 

 procedure agreed with fair accuracy. Any variation in procedure, 

 however, caused very large differences in the result. For example, 

 vigorous shaking during cooking decreased the viscosity as much as 

 50 per cent. Variations in temperature and time of cooking also 

 caused appreciable deviations. The results are graphically given in 

 Figure 2. 



The concentration of starch solution necessary to produce a defi- 

 nite hydrogel when cooled was determined by pouring 10 cubic cen- 

 timeters of the hot starch solution used for determining the viscosity 

 into test tubes one-half inch in diameter. The tubes were placed 

 in water at about 18° C. and allowed to remain unagitated . f or one 

 hour. They were then inverted. The minimum concentration neces- 

 sary to keep the mass from flowing down the inverted tube was 

 termed its "gelling strength." The gelling strength of cornstarch, 

 tree-fern starch, and arrowroot starch was found to be 4.25, 5, and 

 5.25 per cent, respectively. 



