Germination of Spores and Early Stages in Development of Gametophyte of Marchantia polymorpha

1. Spores of Marchantia polymorpha are available in this general latitude, depending upon the climatic conditions, from early July to the middle of September. 2. Elaters of Marchantia are sister cells of sporogenous cells which undergo five divisions before the spore mother cells appear. 3. The ratio of the number of elaters and spores is 1:128. 4. The total number of spores in a single head is estimated to be about 7,000,000. 5. The spores are viable for about a year. 6. One (rarely two) primary rhizoid appears after the growth of the spore and chlorophyll development has occurred. 7. Under ordinarily good conditions for germination, cell divisions giving rise to a very short filament are followed by cell divisions in a second plane. 8. Branching of the young thalli is not uncommon and sometimes occurs at a very early stage. 9. A marginal row of meristematic cells is early established, and these, rather than a single apical cell, are active throughout subsequent development. 10. By differential growth of the cells in the marginal row, a notch appears in the apical region when the young gametophyte comprises 30-40 cells. 11. Dorsiventrality and anchorage are established by the budding off of rhizoids behind and in a line perpendicular to the apical notch, and by the rise of mucilage cells on the lower side of the apex. 12. Excepting during germination, when more moderate light seems better, 13-15 hours of light of good intensity is the optimum. 13. The optimum temperature conditions for vegetative growth are 18⚬-22⚬C., and the optimum temperature conditions for fruiting are 10⚬-15⚬C. 14. As a medium for successful germination and growth, a solid substrate is much better than a liquid one.