I I 2 
H. Hamshaw Thomas. 
Zeiss are of the greatest service in the examination of these and 
similar opaque objects. Even if the sporangia cannot be clearly 
made out, preparations of the spores can be readily obtained. 
The cutinised exospore wall seems to be almost indestructible and 
if embedded in a suitable matrix remains unaltered for an indefinite 
period and can be obtained by dissolving away the surrounding 
material. Thus spores can be obtained from Carboniferous and 
Jurassic plants by treating them with Nitric Acid and Potassium 
Chlorate in a similar way to that used for the leaf-cuticles. If the 
sporangia are small it is best to remove them from the rock with a 
needle and place the fragments on a glass slide possessing a small 
concavity. A drop of Nitric Acid and a few tiny crystals of KC10 3 
are placed on the fragments and the slide is put under a small 
bell-jar with a dish of water, or between two watch glasses the 
lower of which contains some water. In this way it may be kept 
for a day or two without the acid drying up. When the carbonaceous 
fragments have turned brown they are carefully washed with water 
and a drop of dilute ammonia is added. This at once dissolves away 
the opaque material and the spores are liberated. The spore-walls 
show the markings they originally possessed, and the tetrahedral 
or lateral scar indicating their mode of origin is usually 
seen. The preparation and permanent mounting of spores in this 
way requires very cautious manipulation, but by using a glass slide 
on which the whole process is carried out, the progress of the 
reaction can be watched under the microscope. The fact that 
microspores are preserved in this way is most useful, especially 
when we are dealing with structures which appear to be like 
sporangia, for we can easily test whether they are really of this 
nature, and whether they are micro- or macrosporangia. It appears 
as though the megaspore membrane were cutinised in the same way, 
and if we apply the same method of treatment to seeds it is 
remarkable how many tissues become visible and seem to have 
escaped destruction. In some such seeds the outside of the 
integuments, the megaspore membrane and remains of fibrous cells 
been visible ; traces of thickened hypodermal cells and portions of 
tracheids may also be seen occasionally. 
Cedar-Wood Oil. 
The examination of indistinct or badly preserved opaque objects 
under the binocular microscope is often facilitated by the use of 
cedar-wood oil and strong illumination, A drop or two of oil placed 
