626 Timber lake, — Starch-Formation in 
differentiation occurs in such a fashion that the long axis 
of the second grain is at right angles to that of the first: 
that is, a second segment is cut off from the pyrenoid with 
the plane of cleavage at right angles to that in which the 
first grain was cut off. This rule is not invariable, but I have 
never, for example, found a second grain formed between the 
first and the remainder of the pyrenoid. Of course it is 
impossible to establish, with any certainty, the sequence in 
which any great series of grains have arisen such as are shown 
in Figs. 1-4 ; but the general arrangement would seem to 
support the above statement. So far as the pyrenoid itself 
is concerned it is hard to understand why a second grain 
should not follow the first on the same side. Still the pro- 
cess as followed here is better adapted to secure an equal 
distribution of the starch through the cytoplasm, and this 
fact may have led to the establishment of a more or less 
fixed order in the formation of the grains as described above. 
It is possible, too, that the formation of the starch depends 
upon the action of the surrounding cytoplasm as well as of 
the pyrenoid itself. In this case when a starch-grain is fully 
formed it would separate the two and thus, perhaps, lead to 
a shifting in the place of formation for the next grain. 
When the process of starch-formation is going on very 
rapidly, the grains, as they are formed, are continually crowded 
outward by the later-formed grains, so that finally, as pre- 
viously indicated, they are densely packed through nearly the 
whole protoplast (Figs. 1 and 2 6) 0 This condition is undoubt- 
edly what led to the distinction made by Schmitz, and later 
worked out in more detail by Klebs, between starch formed 
around the pyrenoid (pyrenoid-starch) and that formed in 
other parts of the chromatophore (stroma-starch). But that 
there are not two kinds of starch, at least in their origin, 
is made clear by an inspection of Figs. 1-5. It is to be 
noted in these cases that no distinction whatever can be made 
between the starch immediately surrounding the pyrenoid 
and that farther out in the cytoplasm. Moreover, the form 
and arrangement of the whole mass of starch-grains, as shown 
