Ripe pollen structure and histochemistry of some gymnosperms

Some aspects of pollen cytology at dispersal were studied in 12 species of gymnosperms. The pollen grains differed in: 1. volume and cell number; 2. polarization of external structure and internal cell components; 3. wall thickness, especially of the intine, and the resulting percentage of cell volume with respect to total pollen grain volume; 4. stratification and chemical nature of the various intine layers; 5. nature and location of polysaccharide reserves; 6. morphological differences between the dry and hydrated states and phenomena related to hydration; 7. presence and site of orbicles. The various characters are compared and discussed in relation to the length of the reproductive cycle and the relations between the male gametophyte and its female counterpart.