1. The application of the electron microscope to the study of pollen grains is discussed.
2. Two carbon replica methods suitable for the study of pollen grain surfaces are briefly described.
3. Examples are given of the surfaces of various pollen specimens, and a distinction between the submicroscopic structures of Corylus and Myrica is reported. Structures within the furrows of some grains are described.
The high resolving power of the electron microscope is of considerable value in the study of pollen, and the sub-microscopic structure revealed is of interest in problems of identification and of pollen morphology. However, the difficulties encountered in the preparation of pollen specimens for the electron microscope have limited the amount of research carried out in this field.
Pollen grains cannot be examined directly in the instrument because of their size and consequent density to electrons, and even in the case of acetolysed grains the remaining wall is still far too thick to allow the passage of electrons through it. It is therefore necessary to employ either thin sections or surface replicas. The first method has been used extensively by Mühlethaler (1953), Afzelius, Erdtman and Sjöstrand (1954) and Afzelius (1950) in studies of pollen and spore walls. Surface replicas have been employed by Mühlethaler (1955) who used the carbon replica method (Bradley, 1954a). The present author has also made some preliminary studies using this technique (Bradley, 1956). This paper is concerned with the potentialities of the carbon replica in the study of pollen grain surfaces.