An improved cellophane method for in vitro germination of recalcitrant pollen.

The cellophane technique of La Cour and Faberge has been improved by the use of a booklet of filter paper. The booklet consists of seven squares of filter paper stapled together; the cellophane on which the pollen is germinated is placed between the two top leaves of the booklet and the whole soaked in a sucrose-based nutrient medium for 15 min. This arrangement keeps the cellophane flat as it absorbs medium. The top leaf of the booklet is then removed, the pollen dusted on it and the completed preparation closed in a plastic-wrapped Petri dish. The lower leaves of the booklet keep the cellophane moist for up to 24 hr. Proportions of pollen grains germinating are at least as high as in the hanging drop method; pollen of species that germinate poorly or not all in hanging drops do well in this technique. Because the pollen tubes adhere tightly to the cellophane, staining, observation, and studies of various sorts are facilitated.