26 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9 
the cell, some must inevitably be carried out through the opening and lost, 
while others would be near the puncture when the movement ceases. 
Even if several nuclei are lost, a sufficient number remains to maintain 
the vitality of the cell. In a Spirogyra cell which was punctured the single 
nucleus was carried through the hole and no recovery followed. Although 
the hole was small and the protoplasmic loss slight, the cell failed to recover 
its turgidity. 
In Vaucheria the extremely thin membranous walls give so easily under 
the pressure of the needle that it is very difficult to puncture these walls 
unless the cell possesses a high degree of turgor. This is also true of Spiro- 
gyra, although the wall is much thicker. The tough walls of Spirogyra are 
the most difficult of any I have attempted. On the other hand, the walls of 
Chara, Nitella, and Chaetomorpha have a certain amount of rigidity in 
their structure which greatly aids in puncturing. There does not seem to 
be any relation between the type of wall and the viscosity of the enclosed 
protoplasm. Chaetomorpha, with its heavy, striate wall, has a thin, miscible 
protoplasm, while Cladophora, with an equally heavy wall, has very dense, 
nonmiscible contents. 
It has not proved possible to estimate the total amount of protoplasm 
which may be lost by the injured cells. That this loss may be very large 
in some cases is evidenced by the fact that Nitella cells can be punctured 
six or seven times in an hour and still recover. There are no visible ill 
effects from the loss of protoplasm, and future growth appears normal in 
every respect. If the culture becomes infected with either bacteria or 
molds, the punctured cells do not seem any more susceptible than the unin- 
jured. Yet, if the plants are placed in an unfavorable environment, the 
injured cells are always the first to succumb, indicating that there has been 
a lowering of their vitality. 
I wish to thank Professor R. A. Harper and Professor F. O. Grover for 
their interest and encouragement during the progress of this study. 
Summary 
1. All but one of the algae studied are able to heal a wound. 
2. The density of the protoplasm varies from a very liquid condition 
in some species to a quite viscous condition in other species. 
3. No correlation was discovered between the density of the protoplasm 
and the character of the cell wall. 
4. The exuded protoplasm may or may not be miscible with water. 
5. If the exuded protoplasm is nonmiscible, the film formed over the 
escaping protoplasm is not comparable with the plasma membrane. 
6. The puncture is not closed by a film or membrane but by an accumula- 
tion of plastids, pyrenoids, and starch granules in the opening. 
