6io Wolfe. — Cytological Studies on Nemalion. 
The contents of adjacent cells are united by means of the characteristic 
protoplasmic connexions usually conspicuous in these -plants, and in each a 
chromatophore, surrounding a body which has been called a pyrenoid, and 
a well-defined nucleus are present. 
The nucleus occupies a characteristic position in the basal portion 
of the cell just below the chromatophore. Its structure is a matter of con- 
siderable interest, inasmuch as not the slightest indication of a reticulum 
has ever been seen, the chromatin being collected in a single, large, densely 
staining, centrally placed £ nucleolus.’ The nuclear wall is somewhat remote 
from this body, extremely thin and usually difficult to differentiate, and, 
moreover, connected with the nucleolus by means of delicate radiating 
fibrillae. 
The cytoplasm forms a finely granular layer closely applied to the inner 
surface of the wall, and extending throughout the cell, envelops the nucleus 
together with the intricately constructed chromatophore, between the 
processes of which are left vacuoles of irregular contour (Fig. 25). 
Structure of the Chromatophore. 
By far the most striking member of the cell in both living and prepared 
specimens is a highly complex structure, the chromatophore. In the living 
condition the chromatophore is seen to consist of a centrally placed ellip- 
soidal body more deeply pigmented than the numerous strands which 
radiate from it in all directions. These strands, which are of the same 
material as the central body and continuous with it, as they approach 
the cell-wall flatten out gradually on all sides, forming a continuous 
membrane which lies just within the peripheral layer of cytoplasm, and 
is clathrate through the presence of numerous openings, as seen in Fig. 24. 
These unpigmented areas thus represent breaks in the continuity of this 
peripheral portion of the chromatophore, the substance of which is not 
sharply delimited from the surrounding cytoplasm, and the transition from 
the one to the other is thus somewhat gradual, the distinction in nature 
being less abrupt than is represented in the figure. Nothing was observed 
which appears to indicate that there was a difference either in composition 
or structure between the various portions of this complex organ other than 
that of relative density, the material being denser in the central body and 
gradually becoming less so toward the periphery. 
Material crushed on the slide and stained in safranin and gentian- 
violet shows that this central body is not a homogeneous solid. Sections 
reveal more clearly a wall layer of the same material as the rest of the 
chromatophore, surrounding what appears to be a mere vacuolar cavity. 
This vacuole represents the so-called pyrenoid, which earlier writers have 
described as characteristic of the vegetative cells of this plant. In the 
effort to differentiate the substance of this £ pyrenoid 5 a great number 
