STRUCTURE OF STARCH GRANULES. 315 
and consequent expansion of the outer cell-wall or mem- 
brane; these gradually increase in length, exposing the 
interior to view, and allowing the granule to expand later- 
ally till they almost reach the edge of the greatly enlarged 
granule, when, of course, the band of the cell, which has 
still retained its cellular or enclosing character, gives way, 
and the granule assumes the aspect previously described 
as immediately resulting from the application of a strong 
alkali or mineral acid. It is worthy of notice that, while 
these fissures are extending, the strip of membrane be- 
tween any two, still retains the striz, which are clearly 
visible. Now these fissures are, undoubtedly, not in the 
body of the grain, but are merely fissures of the outer 
layer or investing membrane; at least they appear to me 
to be so; and if such should be the case, I would suggest, 
it is a positive proof that these strize do not arise from the 
existence of concentric layers, nor even from an unfolding 
of the outer layer, since they appear even if it has been 
rent by distention. 
“That this exterior membrane or investing layer is of 
a different nature from the contents it encloses, I think 
no one can doubt who has observed the above described 
phenomena; but from what Dr. Gregory says, it would 
appear to be merely a difference of structure or texture, 
' not of chemical composition; and after a careful consi- 
deration of my experiments, I am inclined to attribute the 
striz to the circular deposition of rings of starch on the 
inner surface in precisely a similar manner to the deposi- 
tion of circular or spiral rings of woody fibre on the sides 
of the so-called annular and spiral ducts in the tissue of 
many plants, more particularly those belonging to the 
natural family of Cucurbitaciz, Orchidiz and Filices. 
Drawings of the cells found in the leaves of species of 
Oncidium might easily be taken for representations of 
starch granules, so exact is the resemblance. 
VOL, XV, rT 
