The thelypteroid fern Thelypteris Papilio (C. Hope) K. Iwats. (Thelypteridaceae) is widely distributed in tropical, subtropical and warm temperate regions. The chromosome counts made so far from India are diploid sexual (n=36) (Loyal 1961, Khullar et al. 1988, Manickam 1984, Manickam & Irudyayaraj 1988, Raj & Manickam, 1987). Tetraploid sexual cytotype has been reported only from Sri Lanka (Manton & Sledge, 1954). In the present study Octoploid cytotype (n=144) of this plant collected from Kolli Hills, Tamilnadu, was observed for the first time Thelypteris papilio (C. Hope) K. Iwats, the tropical Asian thelypteroid fern, is cytologically known from India and Sri Lanka only with the presence of diploid sexual in India (Western Ghats and Western Himalayas) and the tetraploid sexual in Sri Lanka. The Sri Lankan tetraploid plant, Christella papilio var. repens Sledge, has also been treated as Thelypteris sledgei Fraser- Jenk. In India, this species is distributed in Eastern/Western Himalayas and Western Ghats. During the recent exploration of pteridophytes on the Western Ghats of Goa, India, the tetraploid cytotype of Thelypteris papilio with erect rhizome has been cytologically confirmed with the presence of 72 regular bivalents in Spore Mother Cells. The cytological data from North India, South India and Sri Lanka shows the latitudinal pattern of distribution of the diploid and tetraploid cytotypes. Thus, tetraploid cytotype is present in Sri Lanka towards the equator with tropical climate in contrast to the diploid cytotype which is present in the Western Himalayas, little away from the equator with temperate climate. Interestingly, on the Western Ghats, the diploid cytotype is present on Southern Western Ghats (Tamilnadu) in contrast to the tetraploid cytotype on the Northern Western Ghats (Goa). Since the cytomorphological characters (rhizome and ploidy) are not consistent with the discovery of the present tetraploid cytotype with erect rhizome, the treatment of tetraploid cytotype with creeping rhizome as distinct species is not valuable.