Nov., 1922] SPONSLER — STRUCTURE OF STARCH GRAIN 
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3. The concentric layers in the spherocrystals are visible because the 
space between the trichites varies. This might be the cause in the starch 
grain also. 
4. The layers are due to periodic changes in the mother-liquor, which 
affects the growth and form of the trichite in both the spherocrystals and 
the starch grains. 
These comparisons and conclusions, based to a great extent upon experi- 
ment, led Meyer to conclude that the grain is a spherocrystal. Only a few 
investigators have opposed this theory; many have accepted it. 
H. Fischer (35) found the dark-cross phenomenon in hardened mucilage 
of certain orchids, and Strecker (36) found the same effect in the guard 
cells of the stoma. Czapek (37) considered both of these cases to be due 
to symmetrically distributed tensions and inferred that the dark cross of 
the starch grain might be due to similar causes. 
Reichert (4, p. 82) in his large monograph on starch accepts the sphero- 
crystal conception without question. 
Perhaps the latest bit of evidence in this connection is from work done 
with X-rays. Herzog and Jancke (38) reported a crystalline structure for 
both cellulose and starch, although no details of their work with starch 
were given. The method they used is one by which it is possible to deter- 
mine whether a powdered substance has an amorphous or a crystalline 
structure; also, if the latter, to determine the crystal system, although in 
certain systems the problem becomes very complex. Further, in many 
instances it is possible to determine the location of the different kinds of 
atoms which make up the crystal. 
That method is the one used for the experimental work which was done 
for this paper, and is described in detail below. 
The X-ray Method of Determining Crystal Structure 
The method consists, briefly, in photographing the X-rays which are 
reflected from the various atomic planes of a crystal. In order to explain 
this method it may be of advantage to have some of the concepts which 
will be used described in terms of present-day science. 
The Crystal 
Since 1850, the face of a crystal has been considered an indication of 
its internal atomic structure (39). No direct evidence of this was brought 
forward until Laue (40) in 1912 conceived the idea that if X-rays are actually 
electromagnetic waves, they should show interference phenomena when 
reflected from a crystal, since the size of the waves approaches the magnitude 
of the distance between the atoms of a crystal. He worked out the mathe- 
matical part of the problem, and Friedrich and Knipping (41) proved 
• experimentally the correctness of his figures. From this brilliant beginning 
the structure of many crystals has been determined; resulting in the 
