Hope . — The ‘ Sadd ’ of the Upper Nile . 509 
in the rains. And he does not think it is an annual, at least 
in cultivation, if kept very moist or in water, as he kept the 
same plant growing for some years at Ootacamund in the 
Nilgiri Mountains, 7,000 feet or so above the sea. Mr. C. B. 
Clarke, who, in the Transactions of the Linnaean Society 
published a ‘ Review of the Ferns of Northern India/ notes 
regarding this fern : — ‘ In rice-swamps, floating ; but much 
more commonly erect, tufted, in ditches, or even in dry spots 
during the rains. The floating and erect forms both produce 
their barren and floating fronds. In ditches the rhizome is 
somewhat creeping and stout.’ T. Moore wrote: — ‘Either 
floating or attached to the soil in shallow, still, or slightly 
moving waters.’ The plants in the Bahr-al-Ghazal must be 
quite off the ground. The present writer found the plant 
growing gregariously in the Dehra Dun, North-Western India, 
in briskly running shallow water, and there it was well-rooted 
in the ground, and liable to be submerged with the rise of the 
water. In Florida, U. S. A., it is recorded as floating. The 
late Rev. C. S. Parish found C. thalictroides growing in his 
garden in Maulmain, Burma, on gravel walks during the rainy 
season ; and the late Mr. H. C. Levinge, a very distinguished 
amateur collector of Indian ferns, gathered it ‘ on an old wall 
at Siliguri in the Darjiling Terai.’ 
Vegetation in the Swamps of Lower Bengal. 
When consulted as to the plants which form the Nile ‘ Sadd,’ 
Mr. Clarke was led to think back to his life long ago, in 
Lower Bengal and Assam, when in the course of duty he had 
to travel about in a boat through the great swamp which 
extends over the zillas (counties) of Sylhet, Comilla, and 
Maimensingh. These water plants of many sorts unite to 
form not only barriers in streams, but, during the annual 
floods of the Ganges, Brahmaputra, and Surma Rivers, a 
dense mass of floating vegetation, extending perhaps 100 miles 
from east to west, and as much from north to south ; and 
Mr. Clarke very kindly furnished some notes in which he 
contrasted the conditions prevailing in Bengal with those on 
