Studies in the cytology and physiology of pollen.

The structure and function of pollen have long been subjects of curiosity and speculation. Even before the concept of sexuality in plants was generally accepted (see Wodehouse, 1935), natural scientists such as Nehemiah Grew and Marcello Malpighi had recorded observations on pollen morphology and hinted at some possible functions of pollen. Wodehouse (1935) quotes from Grew's \Anatomy of Plants\" published in 1682 and from Malpighi's Opera omnia (1687) pointing out the comparatively high degree of accuracy in their descriptions of pollen but at the same time revealing their uncertainty at its \"higher purpose\". A few sentences from these works serve to illustrate attitudes to botanical investigation at that time. Describing pollen grains Grew says: \"The Particles of these powders though like those of Meal or Dust they appear not easily to have any regular shape; yet upon strict observation especially with the assistance of an indifferent Glass it doth appear that they are a Congeries usually of so many perfect Globes or Globulets; sometimes of other Figure but always regular. That which obscures their Figure is their being so small: In Dogs-Mercury Borage and very many other Plants they are extremely so. In Mallows and some others more fairly visible. \"The Colour of these small particles contained in the Theca is also different. But as that is usually white or yellow so are these: sometimes Blewish; but never Red. And sometimes not of the same Colour with that of the Theca. Which further shows how scrupulous Nature is in differentiating the Tincture of the several parts.\" Although not as detailed Malpighi's descriptions were essentially similar to those of Grew. However he tended to interpret the function of pollen in terms of human physiology: \"The pollen dust is likewise a mere secretion.. .prior to the .maturation of the ovum.. .and may be compared perhaps to the menstrual discharge of women.\" Few advances in the study of pollen were made during the next century and a half. Further work was forced to wait upon improvements in microscopy made towards the turn of the eighteenth century."