28 THE AQUAVIVARIUM. 



is easily known by its upper leaves floating on the 

 water, and two or three pairs of them forming 

 a little green star hence its name. This plant 

 forms a pretty object under the microscope, for 

 its leaves and stem are covered with very minute 

 rosette-shaped bodies, which seem to supply the 

 place of hairs in other plants. There are other 

 species of Water Starwort in England, but they 

 are much more rare. 



THE HORNWORT (Ceratophyllum demersum), Fig. 5, 

 is a floating plant, that will live very well in the 

 Aquavivarium, and be found useful in oxygen- 

 ating the water. It is not uncommon in slow 

 streams and ditches. Its flowers are incon- 

 spicuous, but it has long, slender, filamentous 

 leaves, which are arranged in whorls around the 

 stem, and are forked two or three times. The 

 whole stem looks very feathery and graceful. 



II MONOCOTYLEDONOUS FLOWEBING 

 PLANTS. 



VALISNERIA SPIRALIS demands our first notice 

 amongst the Monocotyledonous plants (Fig. 6). 

 Its long leaves with straight veins afford a good 

 example of the nature of the leaves in this class 

 of plants. In Dicotyledonous plants, the veins 

 interlace with each other, forming a net-work. 

 Valisneria is named after Antonio Yalisneri, an 

 Italian physician, who flourished in the begin- 

 ning of the last century, and wrote many works 



/ on insects and plants. Of all the plants we 

 have mentioned, Valisneria is best adapted for 

 growing in the Aquavivarium. It has peren- 

 nial roots, which do not require any great depth 

 of soil, and its long green leaves absorb rapidly 

 the carbonic acid of the water, and in its stead 



