Permanent Preparations from Rapid Cytological Technics

Abstract

Methods of making permanent prepns. from temporary mounts[long dash](1) Pollen mother-cell smears, (2) insect salivary gland chromosome smears and (3) squash prepns. of root tips[long dash]are described. (1) Smeared anthers are treated in the usual way with Belling''s aceto-carmine except that the cover slip is left off. When correct differentiation is attained the stain is thoroughly washed off with 50% acetic acid and the slide flooded with dioxan. This is followed by 2 changes of dioxan for 2 min. each. A drop of Canada balsam dissolved in dioxan is added and a cover slip applied. In cases where a cover slip has been used at the aceto-carmine stage it can be floated off in a staining jar of 50% acetic acid and dehydration with dioxan carried out as above.[long dash](2) The glands are crushed under a cover slip in aceto-carmine on a slide coated with dried egg albumen. After 20 min. the area around the cover slip is flooded with 50% acetic acid and the cover slip floats loose so that it can be removed. The above described dioxan dehydrating procedure is then employed.[long dash](3) Root tips are fixed in some suitable fixative and the Feulgen technic applied. The stained root tips can either be dehydrated by passing through 3 changes of dioxan and mounting in dioxan-balsam where they are divided into small longitudinal sections by sharp needles, or they can be put immediately into a mixture of 1 part of 50% acetic acid to 1 part of corn syrup where shredding with needles is carried out. A cover slip is put on and separation of the cells completed by tamping or by applying pressure to the cover. This squash method is useful with anthers which are difficult to smear when in the early prophase stages of meiosis.