This is usually done by pasting layers of thickish paper, or even thin cards, underneath the blocks.
In England the long barrow usually contains a single chamber, entering by a passage underneath the higher and wider end of the mound.
Byj turning the knob A, placed at the front corner of the stage, a black or white plate, forming a dark or light background, can be swung underneath the specimen.
The fine thread-like filaments composing the mycelium of the fungus are embedded in the tissue underneath and around the uredo-sorus, and draw from the host the nourishment required.
The mercury should be drawn from underneath, for which purpose an arrangement similar to a chemical wash bottle is suitable, and it may be poured into watch-glasses, previously dipped into strong sulphuric acid, rinsed in distilled water, and dried over a Bunsen flame.