Place the glass slide lightly on the stage, with the specimen facing the center of the light hole, press both ends of the glass slide with pressure clamps, and turn the coarse focusing screw with both hands to slowly lower the lens barrel, while observing that the objective lens descends from the side until it approaches the glass slide.

Look at the eyepiece with one eye, and turn the coarse focusing screw at the same time to make the lens barrel rise slowly until the object appears in the field of vision, and fine-tune the fine focusing screw to make the object image clear. Next, move the glass slide, move the object image to the center of the field of vision, and observe the epidermal cells of onion scale leaves under a low-power microscope.

Extended data

Experimental attention

1, onion skin temporary slice, should be made before class, so often add water, keep enough water under the cover glass.

2. Try to choose thin and fresh onion skins and make temporary slices.

3, can be dyed with red ink, drop a drop of red ink on one side of the cover glass, and absorb water with absorbent paper on the other side. Red ink is dyed through onion skin, which makes it easier to observe.