BY THE REV. J. E. TENISON-WOODS. 71 



Pistia stratiotes is found in all the freshwater streams and lakes 

 of Malaysia and the Philippines, covering the surface with plants 

 that look like small lettuces. It floats in rafts bound together bv 

 runners, with roots hanging free in the water or touching the 

 muddy bottom. It is very acrid, but in the Philippines is boiled 

 and used as food for pigs. Blyxa roxhurghii is a submerged herb 

 with long, grass-like, acute and entire leaves, without laminae, 

 tufted, with the flowering peduncles at the bottom of the water. 

 This is spread in the fresh waters of tropical Asia along with 

 Yallisneria spiralis from which it differs in the shape of the leaf 

 and flower. Another submerged herb, but with the radical leaves 

 and peduncles in tufts together on the muddy bottom, and with 

 the leaves bearing a broad lamina, is Ottelia alismoidts, a species 

 found in every stagnant pool throughout Malaysia and the East 

 Indies. Hydrilla verticillata is also common and widely dis- 

 persed in still and running waters, not only in the tropics, but 

 the temj)erate regions of Europe and Asia. The stems are leafy 

 throughout, with short verticillate leaves ; it is much branched 

 and floats under the water in large masses, where it has proved 

 fatal to many a swimmer. Finally Monochoria vaginalis is an 

 aquatic herb common in the rice-fields and ditches, with radical, 

 petiolate, cordate leaves, and racemes (apparently springing from 

 the side of a petiole) of several rather large bright blue flowers. 

 It is employed in Indian pharmacy in liver complaints and stomach 

 diseases. Rubbed down in butter and eaten, it is thought to 

 remove redness of the eyes ; powdered and mixed with sugar it is 

 administered in asthma ; and when chewed is said to relieve 

 toothache ; brayed with milk it is given in fever ; and finally, 

 when young is eaten as a vegetal >le. It is very abundant in 

 ditches around Thaiping, Perak. The other members of the pond- 

 weed families including the Grass-wrack, the Eel-grass, Duck- 

 weed, Water-plantain, Cat-tails, Arrow-heads and Flowering-rushes, 

 have nothing special about them. Azolla rubra is a common 

 minute aquatic cryptogam which completely covers the surface of 

 the water with a purplish-green crust. 



