MIDLAND NATURALIST 27 
Abbe has shown that by transmitted light ‘diffraction images are 
obtained and refraction images by reflected light. Not to enter 
into a discussion of these different imagesit suffices tosay that the 
author had spent hours at a time trying to catch a glimpse of the 
striae and invariably failed, until one day a lucky accident brought 
them to view. On this occasion while working near a window 
through which the direct sunlight happened to strike the top of 
the stage of the microscope, a sudden accidental movement so 
placed the stand as to exclude the light from the mirror. The 
direct sunlight fell on the edges of the drop of immersion oil and 
immediately the markings came out clearly, sharply, and unmis- 
takably. After a certain amount of experimentation it was found 
that the best results were obtained when the incidence of the direct 
sunlight took place as nearly as possible parallel to the stage, the 
microscope being inclined for the purpose, and at right angles to 
the striae. From this it would seem that the lines are alternate 
ridges and depressions on the diatom shell and the lines were 
brought out as contrasts of ridges with their shadows. The 
method is so easy and simple that the merest beginner in microscopy 
could bring out the markings without any difficulty. The method 
has been used with great advantage in our laboratories in deter- 
mining the markings on the spores of the Myxomycetes, as this 
characteristic is at times an important factor in the determination 
of these plants. , 
Notes on Histological Technique. 
I. A SIMPLIFIED MODIFICATION IN A STAINING METHOD. 
J. HUERKAMP. 
The usual method of staining plant tissues with Delafield’s 
haemtoxylin and saffranine as descri in the common texts of 
histology and microtechnique, requires that the preparation remain 
in the latter stain about 12 hours in order that sufficient and 
satisfactory penetration of the color may result. Tissues of certain 
plants will take the stain much more rapidly and retain it more 
tenaciously, while others even after being kept in the stain longer 
than is ordinarily required can not be made to keep it at all. 
