Morphology of Rumex Crispus

Abstract

1. Organogeny is normal, with slight delay in appearance of petals and carpels. 2. The megaspore mother call produces a tetrad of megaspores, the innermost of which functions. The haploid chromosome number is 32. 3. The embryo sac is of the ordinary 8-nucleate type. 4. Microsporogenous tissue is formed from the primary sporogenous cell by 3-4 successive divisions, and reduction is normal. The haploid chromosome number is 32. 5. The mature pollen grain contains two male nuclei, the progeny of a definite generative cell. 6. There is good negative evidence both for and against the occurrence of fertilization. This raises the question whether some of the megaspore mother cells may not undergo reduction, while others only simulate reduction and give rise to a diploid embryo sac, the latter only producing embryos by the apogamous development of the egg. 7. Widespread degenerations occur: (a) in any or all of the anthers, at any stage from the sporogenous initial to the maturepollen grain, and may involve only the sporogenous tissue and its products, or the entire anther; (b) in the ovary, at any stage from the functioning megaspore to the maturing fruit, and may involve only the embryo sac, or both embryo sac and ovule, or the entire ovary; (c) in entire inflorescences. 8 Most pollen grains undergo cytolysis, with abundant starch formation, conspicuous enlargement, and the formation of "pollen tubes." 9. Only a small percentage of pollen grains and embryo sacs have the appearance of being functional. 10. An unidentified fungus invades the anthers after dehiscence, ramifying among but rarely penetrating the pollen grains. 11. There is a definite abscission layer near the base of the peduncle, cutting off either before or after blooming those flowers in which both stamens and ovary are early involved in strong degenerations. There is also a degeneration of the filament cells, severing the maturing anthers. 2. Four types of mature flowers are produced by these degenerations: (a) physiologically staminate, although the pollen may or may not be functional (the ovary is functionless); (b) physiologically ovulate, the stamens having been completely eliminated by degeneration; (c) bisporangiate, having both stamens and ovary functional (very rare); (d) completely sterile, having functionless ovary, and stamens completely eliminated. 13. It is suggested that these degenerations may be Of widespread occurrence, and probably are the cause of (a) dicliny, and finally dioecism, and (b) apogamy, and that (c) they favor the development of successful methods of vegetative propagation. 14. The cause of such degenerations is as yet unknown. It is suggested that deficient nutrition, excessive mutation, and hybridity bear no causal relation to degeneration, except as they may create physiological conditions favorable for it.