Evidences of Hybridism in Selaginella

Some aberrancies of habit were observed, such as bifurcated cones and reversion of the cone at the apex to a vegetative condition. 2. The method of spindle formation in both megaspore and microspore mother cells is very different from the usual one in plants. The spindle fibers appear in the cytoplasm while the nucleus, in synapsis, is at the periphery of the cell. Later the nucleus returns to the center of the cell and is enveloped by the broad spindle. 3. The mother cells are lacking in concerted action and many fail to divide. 4. The study of meiosis is difficult for three reasons: the scarcity of divisions; the extreme smallness of the mother cells; and the quantity of chromatin-like bodies frequently found in the cytoplasm, which in many instances cannot be distinguished from chromosomes. 5. In S. amoena the heterotypic division is irregular. 6. In S. apoda the heterotypic division is often slightly irregular. 7. Two aberrant types of division are predominant in S. mandaiana: (1) the contents of the nucleus pass out into the cytoplasm, the cell divides somewhat quantitatively, and new nuclei are organized; (2) the nucleus elongates and the chromatin is divided without chromosome formation. 8. S. rupestris, which is apogamous, is almost exclusively megasporangiate, has a comparatively high chromosome number, and forms its microspores in dyads like many apogamous angiosperms. 9. There is a large percentage of sterility in the spores of the species of Selaginella examined. Collapsed microspores, microspores devoid of contents but with perfectly sculptured exine coats, megaspores and microspores with discolored exine coats, small granules of exine material scattered through sporangia, and collapsed sporangia are common features. 10. No advanced stages of development of male gametophytes were seen except in occasional spores of S. apoda.