CALYCIP^LOR^ 215 



Bengal by the genus Myriophyllum tuberculatum and 

 M. indicum. The former is characterized by float- 

 ing or submerged stems and highly-dissected sub- 

 merged leaves, commonly found in the border of the 

 salt lakes and other moist places near Calcutta. The 

 latter is common in tanks. 



The submerged leaves of water-plants, like those 

 of Myriophyllum, are often deeply indented, with 

 filiform lobes like a bunch of fibrous roots. This is 

 an adaptation to environment, enabling the plants 

 to absorb water with its dissolved carbon dioxide, and 

 oxygen, and mineral matters through the leaves, which 

 being highly cut up, afford a larger surface area for 

 absorption. Moreover, they offer less resistance to 

 the current and turmoil often set up in water, which 

 would tear expanded blades into shreds. Such water- 

 plants have, as a rule, very little or no root system, 

 the function of the latter being taken up by the root- 

 like leaves. Compare the water-plants Utricularia, 

 Aldrovanda, and Salmnia (ulki-pana and indur-kani- 

 pana) in this respect. Water-plants again have often 

 intercellular cavities and passages filled with air which 

 serve the double purpose of aerating the plants and 

 also buoying them up, so as to prevent them from 

 sinking into the mud by their own weight. Strength- 

 ening and conducting tissues, such as sclerenchyma 

 and bundles, are very little developed, as they are not 

 required, and the epidermal cells are thin-walled, as 

 there is no necessity for conserving the water-supply. 

 These are the common characters of aquatic hygro- 

 phytes. 



Nat. Order 6. Rhtzoplioracece. — Trees of salt 

 swamps or marshes, leaves coriaceous, opposite, 

 stipulate (interpetiolar), calyx valvate, petals often 

 fringed, stamens definite, ovary inferior or half-in- 



