Jan., 1922] NICHOLS METHODS OF HEALING IN ALGAL CELLS 21 
If the puncture is small, the plastids, loosened from the wall, and the other 
particles moving in the rotating protoplasm do not show any acceleration 
until very near the opening. If the puncture is large (250-300 microns), 
the outward flow is spasmodic, a rapid flow following short pauses until 
the movement ceases. When the puncture is large enough for such move- 
ment, the dislodged chloroplastids and the other particles from every 
portion of the cell are seen to move toward the opening, indicating a very 
general internal disturbance. 
An accumulation of particles in the hole promptly forms a protoplasmic 
plug closing the opening. In most cases the forming of this plug is greatly 
facilitated by an accumulation of the ''spiny bodies" so peculiar to Nitella, 
described by Goeppert and Cohn ('49) and by Overton ('90). These 
bodies form the foundation of the plugs. If the same cell is punctured a 
number of times, the number of spherical bodies finally becomes exhausted, 
and the openings are closed by plastids and starch grains only. The other 
structures described by Klemm ('94), Kiister ('99), and Noll ('99), although 
occasionally seen, do not appear to form any essential portion of the plug. 
When the "spiny bodies" are lacking, the plug is formed primarily of 
plastids and starch grains. 
Many young growing internodes (5 mm. or less in length) were punc- 
tured. These internodes are less turgid than the older cells, and are filled 
with a denser mass of protoplasm. In every case healing occurred and 
growth was resumed so that measurable growth was recorded in twenty- 
four hours. 
Sections made from material killed fifteen minutes after puncturing 
do not show any indication of the formation of a membrane to cut off the 
injured protoplasm. The globular bodies forming the plug are crowded 
at that time into a compact mass closing the opening. The inner surfaces 
of these bodies are still imbedded in the cytoplasm of the cell, and their 
spiny projections are unmodified. Before this material was killed rotation 
had been resumed, and the cytoplasm had been moving normally for 10 
to 12 minutes. As the particles in the flowing protoplasm come against 
the plug they are slightly checked in their movement; and frequently this 
results in a somewhat denser, thicker mass of protoplasm just within and 
beyond the opening. The remainder of the cell does not show any modifica- 
tion in its protoplasmic structure. 
In sections of material killed one hour after puncturing, it is possible 
to detect the new membrane forming (fig. 3). This membrane is clearly 
defined near the cell wall, a short distance back from the opening, but is 
rather indefinite and indistinct toward the interior of the cell. The mem- 
brane does not develop as a uniform, symmetrical invagination, but as a 
very irregular, convoluted film, which may pass between two adjacent 
pyrenoids with their associated starch grains, or over one spiny proteid 
body and outside the next. There is no structural difference visible between 
