AQUATIC PLAN TS 1 89 



as temporary and when the leaves begin to turn yellow should be 

 removed. There are many widely distributed species of Potamogeton, 

 all looking quite attractive in a state of nature, especially P. crispus 

 with curly leaves. They look very tempting, but none seem to sur- 

 vive long in the aquarium except P. dcnsns, and that only when estab- 

 lished just to its liking. 



NITELLA 

 Of the slender-leaved aquatics, Nitella gracilis is one of the best. 

 Figure 172 gives a good idea of its dainty form. It is not freely dis- 

 tributed, but is found occasionally in ponds and streams in the East- 

 ern States, usually attached to bits of stick or stone. From this it 

 receives its popular name, Stonewort. In removing the plant to the 

 aquarium, it is best to take also the base upon which it roots. If 

 placed in a situation to its liking, Nitella prospers wonderfully in the 

 aquarium and is a fine oxygenator. Under the microscope the leaves 

 show the circulation of protoplasm .better than any other plant. 

 Requires plenty of light. 



LUDWIGIA 



Popularly known as Swamp Loosestrife, this plant in about 

 twenty-five species is widely and thickly distributed in North Amer- 

 ica, mostly growing at the edges of streams, like Watercress. Although 

 in reality more of a bog-plant than a pure aquatic, it does well in the 

 aquarium, particularly if kept in the earth of the pot in which it was 

 propagated from a cutting. Propagation is very easy in the green- 

 house. About five short cuttings are placed in a two-inch pot, hav- 

 ing a top layer of sand. This is not done under water, but the pots 

 need to be kept saturated and the air very moist. They soon root, 

 and when they have developed about an inch of new growth should 

 be placed in the aquarium. 



Ludwigia is one of the more important aquarium plants on 

 account of its decorative value and pronounced individuality. When 

 kept in a strong light the under sides of the leaves become a beau- 

 tiful red color. Wild stock is not altogether satisfactory. It throws 

 out too many roots to make a pleasing appearance, and in the aqua- 

 rium becomes attenuated in character. A cultivated variety said to 

 have come from South America is better in every respect and is easily 

 obtained, for it is the kind propagated by dealers in aquatics. As it 

 is sold in the original pots before being plunged into water, it can 

 safely be sent long distances. Growing to a length of several feet if 

 u-ntrimmed, it is suited to large aquaria, but may also be kept small 

 by pinching back. Unlike Anacharis, it should not be trimmed at 



