A Cytological Study of a Few Genera of Amaryllidaceae with a View to Find out the Basis of Their Phylogeny

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1. The present report deals with the somatic study on nine different species, namely, Hymenocallis daphne, Hymenocallis harrisiana, Hymenocallis littoralis Salisb., Hymenocallis rotata Salisb., Hymenocallis concinna, Hymenocallis senegambica Kunth & Bouche, Pancratium zeylanicum Linn., Haemanthus kalbreyeri Baker, Cooperanthes percyi Lanc.
2. Refined techniques involving the use of aesculin and coumarin have been adopted for the karyotype analysis and numerical study of chromosomes of different species investigated.
3. In addition to the presence of normal number in the somatic cells, considerable variation has been observed in the same root-tip tissue, which ranges from as low as eleven to ninety-two.
4. A discussion on the systematic position of the different genera has been made and on the basis of the present cytological data, the classification of Hutchinson is being confirmed.
5. Each genus is characterized by mostly having a constant chromosome number in all its species. Evolution within the genus, in view of the karyotype differences, has been visualized to have been brought about mainly through structural changes of chromosomes and also polyploidy.
6. In view of the chromosome number as well as their general morphology, the three genera Crinum, Pancratium and Hymenocallis have been considered to be much related, their position in the evolutionary scale being assigned as Crinum-Pancratium-Hymenocallis.
7. The significance of structural and numerical alteration of chromosomes within the same somatic tissue has been discussed, and their role in speciation in vegetatively propagated plants has been pointed out. It has been further emphasized that the balances within the tissue in such cases are maintained by the constant ratio involving the absolute amount of chromatin matter and the total amount of cytoplasm present in the tissue as a whole.
8. Discrepancies in the report of the genus Haemanthus by Satô have been considered to be due to structural alteration in chromosomes, observed in the present case within the somatic tissue.
9. An investigation on the hybrid nature of Cooperanthes, claimed to be a hybrid between Cooperia and Zephyranthes, has been carried out, but it has been emphasized that far more convincing data should be forthcoming for establishing its status as a hybrid.