620 Timber lake. — Starch- Formation in 
to the nature and function of the pyrenoid are too well known 
to need more than a very brief review. Schmitz, to whom 
we are indebted for the first authentic description of the 
pyrenoid itself, described it as a spherical proteid body, 
forming a part of the chromatophore and bearing a morpho- 
logical relation to the latter similar to that of the nucleole to 
the nucleus. 
Chemically, the substance of the pyrenoid was considered 
to be similar to the chromatin of the nucleus. But the 
evidence for this view of the chemical nature of the pyre- 
noid was, as Schimper 1 afterwards pointed out, entirely in- 
sufficient. Schmitz believed that there was a genetic relation 
between the pyrenoid and starch in that the pyrenoid substance 
was transformed into starch, the latter, however, being laid 
down in the substance of the chromatophore, and not in the 
substance of the pyrenoid. But in addition to the starch 
thus formed around the pyrenoid, he described its formation 
in other parts of the chromatophore as well. According to 
Schmitz there are two types of starch in the chromatophores 
with pyrenoids, viz. that formed in connexion with the pyre- 
noid and that formed in other parts of the chromatophore 
without reference to the pyrenoid. 
Meyer insisted upon the crystalloidal nature of the pyrenoid 
and that it has no special function beyond that of being 
reserve proteid material. He observed cases in which the 
pyrenoid was angular rather than spherical in outline. 
Schimper agrees with Meyer in the view of the crystal- 
loidal nature of the pyrenoid, but thinks that it has a function 
in the formation of starch, as Schmitz had maintained pre- 
viously. But neither Schmitz nor Schimper were able to 
bring any direct evidence for this conclusion beyond the fact 
that, as they thought, part of the starch is formed in the 
immediate vicinity of the pyrenoid. 
More recently, Chmielewski 2 has described a star-shaped 
1 Jahrb. f. wiss. Bot., Bd. xvi, p. 247. 
2 Ueber Bau u. Vermehrung der Pyrenoide bei einigen Algen. Ref., Bot. 
