Botanists and lovers of flowers will be familiar with the two well-known heterostyle types of Primula vulgaris, commonly known as the Primrose, which are: pin-eyed and thrum-eyed. In figure 1 we see (a) the former type, where the stigma is positioned above the level of the anthers, causing floral visitors to first contact the stigma before removing pollen from the anthers, and (b) the latter type, where the stigma is recessed below the level of the anthers, causing floral visitors to first contact the anthers before the stigma:
This spatial separation of the anthers and stigma serves to reduce self-fertilization between male (anthers) and female (stigma) function'. With the pin-type flower, pollination occurs when they are visited by a large, diverse fauna (e.g. bees), whereas with the thrum-type flower, pollination occurs typically through visits by moths and butterflies.
But there is another type of Primrose flower - the third type: which is the 'long homostyle' - figure 2 - where the anther and stigma are in close proximity to each other, enabling self-fertilization instead of relying on visiting insects for pollination.
With the exception of botanists, most people do not know about the long homostyle type because, to date, it is has been found only in a very small area of Somerset, and in another very small area in the Chilterns. The long homostyle Primula vulgaris, previously unknown to Charles Darwin and botanists, was first found by my late parents, Marian and David Greenham.
Marian and David made the unexpected discovery in the spring of 1939, at which time they were engaged to be married. Remarkably unselfishly - for while Marian lived and worked in the village of West Camel, Somerset, David had been living away, studying at Cambridge - they spent almost all of their Easter holiday collecting many samples of primroses in Sparkford Wood, Somerset, just two miles from their respective, permanent homes in West Camel. And they did this to help a Cambridge University botany graduate friend of my father's, Jack L Crosby, who, as part of his work for his PhD, was researching the distribution of the pin-eyed and thrum-eyed types of Primrose in many parts of the country, enlisting the help of many friends and colleagues around the country. Little did Crosby suspect that a significant discovery was about to be made. And how incredibly lucky it was that Marian and David happened to live near one of the only two now known locations of long homostyles, and that Sparkford Wood was chosen for sampling work!
In published articles, Dr. Jack Crosby explained that my father had found the first homostyle primroses and that my mother, then known as Marian Llewelyn Jones, had sent all the samples to him at Cambridge. I recall my parents telling me about this, except that they said that it was actually my mother who found the first long homostyle.
Many years later, BBC Television twice screened a 30-minute nature programme centred on this discovery. It was introduced by Dr. David Bellamy, and presented by Dr. Crosby, and, much to my parents' amusement, included filmed sequences with actors portraying my courting parents strolling romantically through woodland, occasionally stooping to pick primroses, and all the while dressed impracticably in fine clothes of the period.
My father came to know Jack Crosby while he, too, was at Cambridge University also studying botany. They both completed their PhDs after the end of the Second World War. Jack Crosby made a career out of botanical research, securing a post at Durham University, while my father worked as a scientist at East Malling Research Station, Kent, becoming Head of the Fruit Nutrition Section.
Charles Darwin (1862). On the two forms, or dimorphic condition, in the species of Primula, and on their remarkable sexual relations. Journal of the Proceedings of the Linnaean Society (Botany).
Charles Darwin (1877). The Different Forms of Flowers on Plants of the Same Species. London: Murray.
J L Crosby (April 17, 1940). High Proportions of Homostyle Plants in Populations of Primula vulgaris. Nature, April 27, 1940, Vol. 145. (And references to this in some subsequent articles published elsewhere).
Written in fond memory of my parents, Marian and David Greenham, who married at West Camel in November 1939, and lived in East Malling from 1946 until their deaths in 1991 and 2007 respectively.