1910] LUTMAN—CELL STRUCTURE OF CLOSTERIUM 253 
in the reticulum. The strands from the fine-meshed reticulum sur- 
rounding them seem to come up to these granules and apparently hold 
them in position. These granules in C. Ehrenbergii are usually arranged 
in a fairly compact mass of varying size at the center of the nucleus 
(fig. 1), but they may be scattered out in an irregular manner across 
the long axis of the nucleus (fig. 29). In C. moniliferum (fig. 28) 
these bodies form a mass that is practically spherical, but shows a 
few irregularities on its surface. The nucleus in this species resembles 
that of Spirogyra very much, but it can be made out that the central 
spherical mass is made up of smaller pieces, while in Spirogyra the 
so-called nucleole appears as a homogeneous sphere. 
The real significance of these granules and of the meshwork 
that surrounds them, and the part which each takes in cell division, 
can be determined only by seeing them during the time of chromo- 
some formation. Their behavior will throw light on the nature of 
the so-called chromatin nucleolus of Spirogyra, in which, as described 
by Mirzkewrtscu (14), BERGH (1), and others, is contained all the 
chromatin in the nucleus. I shall discuss the phenomena of nuclear 
and cell division in a further paper. 
My indebtedness to Professor R. A. Harper for his advice and 
criticism during the progress of this work is very great, and I take 
this opportunity of expressing my appreciation of them. 
Summary 
1. The current figures and descriptions of the chromatophore 
of Closterium derived from NAGELI are fundamentally incorrect. 
The chromatophore is not made up of a series of radiating plates 
about a slender central core, but is a curved cone-shaped structure 
with relatively narrow ridges on its surface. 
2. The pyrenoids are imbedded in the periphery of this chromato- 
Phore in C, Ehrenbergii and exactly at its center in C. monilijerum. 
3. Pyrenoid starch and stroma starch both have the same origin, 
all the starch being formed around pyrenoids. 
4. The pyrenoids show considerable internal structure, frequently 
Containing denser and lighter portions, vacuoles, etc., and often are 
cleft into a mass of disks or segments of varying number and form. 
AGRICULTURAL EXPERIMENT STATION 
BURLINGTON, VERMONT 
