Colchicine-Feulgen Leaf Smears

The colchicine-Feulgen leaf smear has many advantages. It (1) prevents spindle formation, (2) allows the chromosomes to be widely spread in the cell, (3) straightens the chromatids, (4) allows the constrictions to become very noticeable, (5) increases the number of chromosome plates by preventing anaphase, (6) facilitates smearing, and (7) stains only the chromosomes. (8) Young leaves are generally easily obtainable, while roots of the proper sort are to be had only under very special conditions. (9) Mitoses are frequently more numerous in young leaves than in roots. The schedule for specimens of Phlox involves a 1 to 2 hour pretreat-ment of young leaves in a 0.2% colchicine solution, fixation in Sem-men's Carnoy (3 vol. absolute alcohol, 1 vol. glacial acetic, 1 vol. chloroform), hydrolysis for 25 minutes in 10% HC1 at 58° C., staining in decolorized fuchsia, smearing in 45% acetic acid, and running the material on slide and cover glass thru acetic alcohols (1:1, 1:3, 1:9), absolute alcohol, xylol, and balsam.