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NOTE ON THE FLOATING ISLANDS OF RIWALSAR.
BY
S. R. Kashyap.
Professor of Botany, Government College, Lahore.
In July 1916, Marietta Pallis published an interesting paper on "The Structure and History of Plav : the floating fen of the Danube" in the Journal of the Linnean Society (Vol. XLIII, No. 291). I believe it is not generally known among botanists that a similar floating fen on a small scale occurs in the Outer Himalayas in Mandi State. The writer had an occasion to visit the place in August 1919 and though it was not unfortunately possible to undertake a detailed investigation of the floating islands or to make a large collection of plants, some interesting observations were however made. This note has been written with a view to induce somebody else with a better opportunity to investigate the place in greater detail.
The islands as stated above are met with in Mandi State in the freshwater lake at Riwalsar, which is for this reason held sacred by the Hindus and the Tibetans (Buddhists) for whom it is an important place of pilgrimage. The lake lies about 10 miles south-west of Mandi, surrounded by hills and some 5,000 feet above sea-level- The Mandi State Gazetteer says practically nothing about the fen. The only information given there in connection with this paper is:—"The circumference of the lake; exceeds a mile and its waters are of immense depth. There are many large floating islands on its surface and this singular fact is attributed to its sancity."
No data are available as to the exact depth of the lake, its circumference or the exact size of the islands.
The first point of botanical interest is that the floating islands are formed by Phragmites like the Plav mentioned above. A few other plants are also met with in addition but they do not contribute much to the formation of the islands.
The total number of the islands is seven. The largest (known as Parbati's island) is, as seen from a distance, of a few yards about 20 yards long and about 4 yards wide and has rounded ends. The others are much smaller. The islands are formed practically wholly by a species of Phragmites, apparently P. communis, which forms very
