NOTE ON THE SECTIONS OF PINNULARIA. 37 
8. Section of cotyledon cleared in potash + 430. 
g. Granules resembling starch, by 1-10-in. homog. imm. ob- 
jective. 
to. Section of soaked seed shell, the ridges swelled up and mem- 
brane raised up from the pits of the surface. 
11. Cells of outer membrane, in glycerine + 215. 
tz. Piece of seed shell macerated in acid; a, cells of the husk; 4, 
ridges of the surface ; ¢, cells of outer membrane, distended ; 
da, cells of inner membrane ; e, true membrane of husk cells ; 
J, separated blocks of the shell. 
13. Appearance of shell and section; a, in water, by %4-in. ob- 
jective ; 6, by 1 in.; 4 macerated in potash; d, in acid; 
é, in acid, by Y4-in objective.—Zhe American Monthly 
Microscopical Journal, 
NOTE ON THE SECTIONS OF PINNULARIA. 
By M. PRINz. 
N the preceding Bulletin I have presented some remarks on the 
subject of a note by M. Burgess* relative to the markings of 
Coscinodiscus Oculus Iridis and of Trinacria regina. M. Burgess 
published in the same work some unpublished designs of the late 
Walker Arnott, representing the structural details of Pinnularia. 
From these drawings, the striz, more or less perpendicular to 
the raphe, which ornament the valves of this diatom, appear to be 
tubes.¢ Their details were studied on fractured edges placed in 
favourable positions for examination. By inspecting the figures of 
this work, it is easy to assure ourselves that their natural sections 
present the same inconveniences as those of the sections of 
Pleurosigma, obtained by M. Flogel, with which we compare them. 
They are too thick and often furnish false images, above all with 
penetrating objectives. 
M. Pfitzer, in his admirable work on the Diatoms,i has given 
a very detailed description of the structure of Pinnularia. It is 
based on the examination of the edges of fractures, and above all, 
of sections made with the razor by a process similar to that of M. 
Flogel, that is to say, sections of diatoms embedded in gum. This 
method does not seem to have given very satisfactory results, as the 
* The Microscopical News, March, 1883, p. 71. 
+ This opinion was also maintained by Schumann (Diatomeen der hohen 
Tatra, Verhandl, d. Zool, bot. Gesell, Z. Wien, 1867, p. 73. 
+} Pfitzer. Untersuchungen iiber Bau u. Entrickelung der Bacillariaceen, 1871. 
