1. A critical cytological investigation of nine species of
Ophioglossum (including several cytological and geographic races), one species of
Botrychium and the monotypic
Helminthostachys has been made.
2. The lowest haploid number for
Ophioglossum is
n=120 and for
Helminthostachys,
n=94.
3. Almost all the species of
Ophioglossum investigated in the present study (excepting the aneuploid series in
O. reticulatum and perhaps
O. vulgatum) are found to form a polyploid series based on the haploid number
n=120.
4.
O. reticulatum L. is shown to have the highest chromosome number yet recorded in any species (
n=c. 630, 2
n=c. 1260).
5. The basic chromosome number of the Ophioglossaceae is postulated to be 15.
6. Evidences of chromosome numbers obtained from this study show the probability that there is some parallelism in the cytological evolution of the Ophioglossaceae and the
Schizaeaceae. Both
Ophioglossum and
Schizaea exhibit very high chromosome numbers. The basic number 15, characteristic of the Ophioglossaceae, is also shared by
Lygodium, the most primitive genus of the Schizaeaceae.
7. Cytological evidence is in favour of regarding
Botrychium as the most primitive of the three genera while
Helminthostachys is intermediate and
Ophioglossum the most specialised.
8. There is no cytological support for the segregation of species of Botrychium and
Ophioglossum into subgenera or for raising these subgenera to generic status.
9. It is suggested that the greater percentage of polyploids as well as higher grades of polyploidy encountered in South Indian races of
Ophioglossum may be related to the fact that Peninsular India is geologically one of the oldest land masses with a continued vegetation cover for a very long geological period. This suggestion is incidentally supported by evidences of chromosome numbers from ancient genera like
Tmesipteris and
Phylloglossum from Australia which also represents a very old geological formation.
10. The taxonomic delimitation in species like
O. reticulatum,
O. petiolatum and
O. vulgatum is seen to be very artificially drawn.
11. Taxonomic revision in the light of cytology is necessary for
O. nudicaule.
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