Identification of Large Grass Pollen
In order to attempt an identification of the various large grass pollen encountered, the long axis of each grain and the pore diameter (including annulus) were measured, and the ratio between the two plotted. Barghoorn, Wolfe, and Clisby (1954) have suggested that this ratio can be used to supplement size measurements in attempting to identify fossil pollen of the tribe Maydeae. However, one can not compare directly the size data from the LoDaisKa fossils with the data from modern pollen assembled by Barghoorn, Wolfe, and Clisby (l.c.). Christensen (1945) has shown that not only do recent and fossil grains of the same species differ in size (depending partly upon the type of sediment in which the pollen is preserved), but also, different methods of preparation greatly affect the size, often differentially with respect to fossil and modern pollen. The recent pollen measured by Barghoorn, Wolfe, and Clisby (l.c.) was prepared by acetolysis and mounted in glycerine jelly. By comparing the size of modern Corylus avellana pollen prepared and mounted in this manner (ca. 28, Christensen, 1945) with the size of fossil Corylus avellana pollen from a variety of sediment types prepared and mounted by the technique used in the present investigation (ca. 24, S. T. Andersen, pers. comm.), one can arrive at a factor (7/6) by which the size of the fossils can be multiplied in order to compare more directly with the data presented by Barghoorn, Wolfe, and Clisby (l.c.). It should be emphasized that such an absolute comparison is dangerous, because there is no way of determining precisely how the environment of preservation at LoDaisKa has affected the pollen, and there is no guarantee that size changes of Corylus and Gramineae pollen are absolutely proportional.
For each grass grain both the long axis measurement and the pore axis ratio are tabulated in the results below. Only fully expanded grains were measured.