NOTE ON THE SECTIONS OF PINNULARIA. 39 
and polishing processes. Such difficulties have probably obliged 
M. Pfitzer to interpret, by a diagram, the result of his observations 
on a certain number of sections. 
At last I have met with, in one of my preparations, a moderately 
thick section of an individual of large size. It is perpendicular to 
the long axis of the diatom, and consequently gives a normal 
section of the raphe taken around the central nodule, that is to say, 
in the thickest part, and the more resisting of the frustule as shown 
in fig. 14. We can apply, point by point, to this figure drawn entirely 
from nature, the complete and minute description of the structural 
details of Pinnularia given by M. Pfitzer. I return then to this 
description, and shall only call attention to the slight differences 
which exist between my drawing and that of the learned German 
botanist. 
The sections of the raphes present, at this place, the aspect 
of crevices running perpendicularly towards the interior of the 
frustule ; these divide the frustule, the ends of which terminate in 
two bends turned in opposite directions. 
I have already said that I have not been able to obtain satisfac- 
tory sections of this organ in remote parts from the central nodule, 
where there it appeared placed obliquely. 
With M. Pfitzer, I believe that the raphidian crevice inclines 
more and more in this place, as it raises itself anew towards the 
terminal nodule. The asymmetry of the central nodules is more 
apparent ; they are also more striking than those which this author 
has drawn. I have in no case perceived any break of continuity 
in these nodules (Schumann); they appear entirely solid. The 
sections of the connectives (hoops), and the slight displacement 
they have accidentally met with, confirm the opinion of Pfitzer 
on their mode of attachment, a mode very common in divers 
kinds of diatoms ; but I have not been able to recognise the deep 
furrow which he says surrounds the connectives. Apart from these 
questions of detail the similarity is complete.* 
To elucidate the nature of the striz or ribs on the valves of 
Pinnularia, I have examined sections made parallel to the long 
axis of the diatom, sectioned by consequence perpendiculary to the 
ribs which furrow the valves. These longitudinal sections are pre- 
sent in great number in the thin plates prepared from the earth of 
Franzensbad, rarely they are defective. When one of these sections 
is too thick it comprises a greater or less portion of the rephidian 
*M. Fliigel has equally studied sections of Pinnularia, but the conclusions are 
only known by a very short resumé which appeared in the Botanische Zeitung, 
1872, p. 741. This able micrographer there describes some types of diatoms 
in section. The Pinnularia is shown in one section, and it is added :—‘‘ A large 
empty space which has only one passage in the form of a short canal towards 
the interior.” 
