1900] BRIEFER ARTICLES 115 
As before stated, Zimmermann inferred the spiral arrangement of 
the material in the walls of the outer cells from the direction of the 
pits, and from the appearance in polarized light; but according to 
him no one had succeeded in bringing out clearly any striation. 
After treatment with strong caustic potash and then with dilute 
glycerine, I found such striations quite wel] marked, passing obliquely 
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FIG. 1. Cross Section of half an awn showing the disposition of the mechanical 
- 2. An isolated cell (dry) showing the spiral arrangement of the material 
n.— Fic. 3. An optical longitudinal section of one of the cells (x) 
2.— Fic. 4. One of the cells after soaking in a macerating agent.— 
deni ae am showing the resultant of forces that may cause torsion in the mechan- 
“~STGS. t, 3, and 4 are enlarged 115 times. 
on me cell (ig. 2). When seen through the cell in the opposite 
side. they pass in opposite direction to those in the wall on the nearer 
(more ae makes patent the spiral structure of the cell wall, denser 
dense, By refractive) layers alternating with layers which are less 
