From “On Pollinating”, published in the Quarterly, Volume 9, July 1951.
[Florence Levy (later Florence Bellis) was the founder of Barnhaven and a founding member of the APS. She was very influential in spreading the understanding and love of primroses world-wide.]
…[The] season is at hand for pollinating and there may be those who wish to embark on this simple and fascinating venture for the first time. For those the following abbreviated procedure is offered as one method of pollinating by hand. Taking the polyanthus as an example, the first step is to select the parents for form, color and size for the eventual attainment of all three. Those plants exhibiting all three characteristics at the beginning of hand pollination produce outstanding results in one or two generations.
When the blossom first unfolds from the bud is the ideal time to pollinate. The stigma is receptive, the pollen is still green, which means that it has not self-pollinated, and there is small likelihood that bees have had a chance to probe for nectar thereby introducing undesired pollen. Emasculation, or removal of anthers from the plant, is simply accomplished by taking hold of the blossom with both hands, tearing it in half and pulling the floret, with anthers attached, from the calyx. This act also removes all attraction for insects.
The blossoms of the plant supplying the pollen, which are necessarily more mature to allow time for the pollen’s ripening, are pulled apart in the same manner and each half of floret held so that the anthers spread apart like fingers. It is then very easy to rub the anthers over the stigma of the seed-bearing parent when held in this position. In this way the stigma is completely coated with the pollen of the intended cross with small chance of foreign pollen finding a foothold. However, in truly scientific work, the pollinated plant is bagged in cellophane or wax paper. Since there are five pollen-loaded anthers to one stigma, an excess of pollen always exists. If the pollen-bearing parent is outstanding enough to warrant its use in fertilizing many plants and there is need to hold it over, the pollen remains potent for days when put in a tightly covered jar and stored in the refrigerator.
It is unnecessary to remark that pollination should be done on a clear day, but even the clearest days in April develop sudden showers, in which case bagging will prevent the rain washing the pollen. Each plant that is pollinated should be labeled according to the cross made. In this way the identity of the seedlings is kept for future breeding purposes.
One of the marks of a well-bred primrose is the thrum-eye, the short-styled type of bloom that has the stigma hidden in the tube and the anthers in full view at the entrance. When crossing a thrum with a thrum, a very large percentage of thrum-eyed children is a natural result. This is called “illegitimate” pollination. Two other illegitimate forms of pollination that are possible but have little or nothing in their favor are a cross between two pin-eyed or long-styled types, and self-pollination. The first would be flying in the face of good form and the second, if continued for any length of time, would result in a loss of vigor. “Legitimate” pollination is the crossing of the long-styled with the short-styled, the pin with the thrum, or vice versa…