70 Establishment of' Vegetation at the Surface of the Globe. 



ed or abandoned basins of water, we find them covered with 

 a greenish scum, which, for a long time, was considered as con- 

 sisting of impurities thrown out to the surface of the water, but 

 which, if observed with more attention, we shall easily be con- 

 vinced, belongs to the vegetable kingdom. The substances of 

 which this scum consists are designated by the names of coriferva 

 and bi/ssi. Duckweeds (lemnas) and callitriches accompany or 

 succeed them. These plants, which are destitute of roots, form, 

 by their interlacement, a sort of floating sward, the remains of 

 which are precipitated to the bottom of the water, and consti- 

 tute the soil destined to receive plants of a superior rank. Af- 

 ter this potamogetons, charas, and myriophylla line the inte- 

 rior of basins and lakes, extend themselves into meadows con- 

 stantly covered with water, and reserved for the nourishment of 

 a great number of aquatic animals. 



In proportion as the bottom is raised, more vigorous species 

 appear above the water, and develope tliose beautiful corollas, 

 the brilliancy of which vies with that of the flowers of our gar- 

 dens. The liquid plain is converted into a parterre embellish- 

 ed with tufts of floating ranunculi, naiads, hydrocharides, val- 

 lisneriae, surmounted by the ample calices of silver, gold or 

 azure of the nel umbos, and nuphars, with broad and varnished 

 leaves, while the sagittariae^ flowering junci, menyantheses, hut- 

 toniae, &c. form upon their edges an elegant and varied border, 

 to which are joined beautiful veronic.^, cenanthae, phyllandrae, 

 surmounted by salicariae, bidentes, eupatoriae, &c. 



Thus the waters, as well as the bare and stony part of the 

 globe, are peopled with vegetables, which convert into marshes 

 those liquid plains upon which have formerly floated the barks 

 of fishermen. These waters gain in surface what they lose in 

 depth, and carry fertility to all the surrounding grounds. In 

 proportion as they are lowered, we see beginning to grow those 

 species which in some measure hold an intermediate place be- 

 tween aquatic and terrestrial plants, such as large gramineae, 

 reeds, poas, carices, scirpi, rushes, typhae, &c., but no plant con- 

 tributes more to the conversion of these marshes into pasture 

 grounds, than the prevalence of certain species of mosses, espe- 

 cially sphagna, which rise in yearly layers above one another, 

 and daily increase in thickness as well as in extent. If these 



