AQUATIC PLANTS 43 



States. If established in soil in flat pots it flourishes in a well-lighted 

 aquarium. Pieces collected from the wild may be introduced by fastening 

 into the sand. They present a very attractive appearance and will last 

 for quite a time, but should only be regarded 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 appear 

 very tempting, but none seem to survive long in the aquarium except 

 P. densus, and that only when established just to its liking. 



NITELLA 



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

 Figure 26 gives a good idea of its dainty form. It is not freely distributed, 

 but is found occasionally in ponds and streams in the Eastern 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 holds. If placed in a position to its 

 liking, Nitella prospers wonderfully in the aquarium and is a fine oxygen- 

 ator. Under the microscope the leaves show the circulation of protoplasm 

 better than any other plant. Requires plenty of light. Not commercial. 



This plant is really an Alga and has no true roots, but " holdfasts." 



LUDWIGIA 



Popularly known as Swamp Loosestrife, this plant in about twenty- 

 five species is widely and thickly distributed in North America, 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 greenhouse. About five 

 short cuttings are placed in a two-inch pot, having 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 submerged 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 beautiful red color. 

 Wild stock is not altogether satisfactory. It throws out too many roots 

 to make a pleasing appearance, and in the aquarium 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 propa- 

 gated by dealers in aquatics. As it is sold in the original pots before 



