52 PLANTS FOR TIIK 



when the petals of their flowers fall, are positively injuri- 

 ous, as the}' add more refuse vegetable matter for the 

 snails and other scavengers to remove. The ferns, from 

 belonging to the class of plants called Cryptugamia, or 

 llowcrless plants, are free from this objection to their use, 

 and are very ornamental when arranged with taste on any 

 rock-work projecting above the water's edge. Mr. llib- 

 berd, in his book called " Rustic Adornments for Homes 

 of Taste," gives us a list of such of these beautiful plants 

 as may be used by way of ornament for our Aquarium. 



TIL riANTS USED FOR AERATIXG, BEING COMPLETELY OR TARTLY 



SUBMERGED. 



Foremost among these truly useful plants, stands the 

 almost universal Aquarium inhabitant, 



Valisxeria spiralis (PI. III., Fig. 2). It is certainly 

 one of the most useful of all the aquatic plants, though, 

 perhaps, not the most ornamental, even of the submerged 

 ones, which are generally thought to be not so graceful 

 in their outline as their relations of the shore. It is 

 found, I understand, at several places near New York 

 city, one of which is at West Point (and is mentioned 

 by Prof. Bailey in Silliman's Journal, vol. xlii. p. 80, 

 note), on the shores of the Hudson River, where we have 

 a curious assemblage of fresh-water and marine vegeta- 

 tion ; the Valisncria, together with Potamogcton, growing 

 just below high-Water mark, and Entcromorpha, Ectocarpus, 

 etc., from that point to below low-water — thus showing 

 that the fresh, being lighter than the salt water, floats, as 



