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. p olarization of external structure and internal cell components; 3. wall thi ckness, especially of the intine, and the resulting percentage of cell volu me with respect to total pollen grain volume; 4. stratification and chemica l nature of the various intine layers; 5. nature and location of polysaccha ride reserves; 6. morphological differences between the dry and hydrated st ates 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 a nd its female counterpart.