Chromosomes from Herbarium Sheets of Impatiens

In northwestern Himalayan species of Impatiens, the pollen grains at shedding possess a crescent shaped generative nucleus in prometaphase from which the chromosome number is easily determined. The fresh or fixed pollen grains are studied by the usual aceto-carmine squash method. The generative nucleus generally remains in the same state in pollen of the herbarium specimens. Anthers from such material are soaked overnight in a saturated solution of iron acetate in 45% acetic acid, rinsed and squashed in dilute aceto-carmine. Preparations are heated several times to boiling. Reliable counts of chromosomes have been made from such slides.