CHAPTER II. 



METHODS USED IN THE STUDY OF STARCHES. 



The methods used in the preceding research ( Publi- 

 cation \". 173) were al its inception sufficiently ati 

 factory to meei the al requin of a purely 



preliminary and exploratory investigation, bul as the 

 [ressed it was found, as was bo be expected, 

 radical improvements could be made in various 

 directions. Advantage has h n of this exper 



ami while the methods continue to he inexact, in the 

 ntional sense, the}' are practically exact so far as 

 3 differentiation an. I recognition of diffi 

 starches are concerned. For obvious reasons the descrip 

 tions of the methods given in the previous research are 

 herein in a large measure repeated, with some omissions, 

 . and additions. 



1. Preparation of the Stanches. 



The starches were prepared from bulbs, tubers, rhi- 

 zomes, bulbils, ami pseudobulbs, all in the resting 

 The specimens were comminuted by the aid of an ordi- 

 nary culinary grater. Four or five volumes of water are 

 added to the pulp, thi ma trained I brough four thick- 

 nesses of cheese-cloth, ami the pulp then washed with 

 sufficient water ami strained a- bef< re. The starch-water 

 nation l- decanted in cylinders ami the starch is 

 -eil by repeated washing and decantation. Finally 

 the starch is collected in shallow dishes, the water as far 

 as possible drained off, ami the preparation dried at 

 a temperature of 50° C. By this simple means starches 

 can he prepared which are with ran' exceptions practi- 

 cally free from gross impurities. To have carried out 

 purification to the extent of practical demineralization 

 would have proven of far gTcater disadvantage than gain. 



■j. Simultaneous Studies ok Starches of the 



PAEENTS AMI HtBETJD AM) OF THE MEMBERS 



of a Genus. 



For obvious reasons, in a comparative investigation 



such as the present it is desirabl simultaneous 



examinations of all three or four starches of a set by 

 one of the various method., of study and to take up the 

 methods seriatim in preference to taking one starch 

 and subjecting it to the entire series of methods 

 studying another specimen; the same plan cum 

 itself when there is a number of sets belonging to the 

 same genus. 



3. Histologic Method. 



This method has been found to be of signal useful 

 ness, and up to recent years it has been the sole reliance 

 in attempts to determine the kind i 

 howevi r, perfectly obvious at the very inception of 



. and rendered clear as far hack as the investi- 



ol I ■ li in L858, that t:. 



iated with others, could not he it' ip°n, and 



that it was liable to '"• absolutely misleading. .'■. 

 differences in form may i • least imply differ* 



in the starch en pointed out in ■ 



chapters of the preceding memoir. Magnification : 

 ing from 35 to 100, ometimes higher, was used, aceord- 

 ing to the size of the grains and incidental conditions. 

 A sufficient amount of dried starch ..-ruinated on a 



slide and mounted in a very dilute Lugol's solution, care 

 taken not to add a larger quantity of iod 



Bcient to late the lamella-. Since stai 



of different sources .-how wide diffi in the intensity 



with which they become 

 convenient to have on hand a number of solutions rang- 



rom I to '.' p.: , a. By the aid of such ordi- 



nary microscopic technique there wfcre recorded the 

 form and size of the grain ; the p ad form of the 



hiluni; the form, number, am! other characteristics of 

 the lamella-; the chara ' pi rtaining I i the form 



of the grains, whether single or in -. triplets, 



aggregates, etc. In de cribing the grains the I 

 "proximal end" and "distal end been ado 



the former being the end nearer which the hiluni is 

 I. The " longitudinal axis th an 



imaginary line, extending from the proximal end through 

 the hiluni to the distal end. In different starches and 

 in different grains of the same kind of starch this may 

 be long or the short axis. The measuri 

 ty of the hiluni have refi 

 the hiluni from the proximal end of the longitudinal 



4. Photomiceogeaphio Records. 



Verbal descriptions of the histological characteristics 



. as fail to r^n\<-\ adequat 



included in the text have therefore been accom- 



! by photomicrographs of the grains lightly colored 



with iodine, as seen in the microscope. In making these 



:is we used an ordinary Bausch and Lomb 



microscope with a f^-inch objective and a 2-inch eye- 



. which gave us a magnification on the rield of 



projection of 300 diame many 



of the more minute feature.-, of the grains will j 



raphs. Moreover, inasmuch as no 

 two fields are alike in case of any starch or slide, the 

 pictures are to he taken as being grossly of an av 

 character of a field. In recording the i .1 de- 



scriptions, especially in form, many 



lid.!- . 



The photomicrographs of the pi .ere 



made by the use of a l' L .-inch -inch 



eye-piece (draw-tube in), or a - live and a 



