ore.. Hitcucock: DIFFERENTIAL STAINING 
These structures were first observed by me on June 18, 1918, 
in a variety of Nitella opaca Ag., found at Ithaca, New York, 
although not recorded in the local flora. Since then I have re- 
peatedly observed them in another species of Nitella, not yet seen 
in fruit, and also in Chara coronata, var. Schweinitzii. From this it 
may be inferred the structures are common to this family of plants. 
The only mention I have found in the literature of anything 
resembling these structures is in an admirable paper by Goeppert 
and Cohn,* where they are rather imperfectly described, not quite 
as I have seen them. Doubtless the description relates to the 
same structures. The authors associated them with the formation 
of starch, , 
IrHaca, NEW YorRK 
SUPPLEMENTARY NOTE 

The long, hyaline rhizoids of Nitella afford a more favorable 
means of demonstrating the selective coloring. The vacuole of a 
rhizoid cell becomes: deeply colored, while the thin, uncolored 
outer stream is in active rotation. 
The remarkable fact, already mentioned, that only living 
cells become colored, is more clearly manifest in the small and 
transparent rhizoid cell. In any mass of rhizoids by far the 
greater number will be dead cells. These remain colorless in the 
dye, while the living cells begin to color immediately. So long 
as cyclosis continues in a cell, that cell will take the color. If the 
cell is dying and the cyclosis is weakening it will not stain so deeply 
as in active life; but whenever a trace of color is seen cyclosis 
can be detected. When cyclosis has ceased no coloration what- 
ever is visible. When a stained cell dies the color soon disappears 
from the vacuole, doubtless by diffusion in the outer water. 
It would seem as though we had in this a test for living matter! 
But what kind of living matter has the vacuole and how does it 
differ from the denser, outer protoplasm? Or, have we instead, 
a test for vitality in a cell? Speculation as to the significance of 
these facts is at present unprofitable. Osmotic action affords no 
explanation of a concentration of a solute by passing through a 



* Ueber die Rotation des Zellinhaltes in Nitella flexilis. Bot. Zeit. 7: 665-673> 
681-691, 697-705, 713-719. pl. 10. 1849. 
