(ECONOMY OF AQUATIC PLANTS. 253 



and all its contents apparently perfect, except that 

 there was only a minute cavity where the embryo 

 should have been, in consequence of the want of an- 

 other tree with stamens, which was not to be found 

 perhaps nearer than Japan. Gardeners formerly at- 

 tempted to assist Nature by stripping off the barren 

 flowers of Melons and Cucumbers, which, having no 

 , germen, they found could not come to fruit, and were 

 therefore, as they supposed, an unnecessary encum- 

 brance to the constitution of the parent plant. But 

 finding that, by such a practice, they obtained no 

 fruit at all, they soon learned the wiser method of 

 admitting air as often as possible to the flowering 

 plants, for the purpose of blowing the pollen from one 

 blossom to the other, and even to gather the barren 

 kind, and place it over that destined to bear fruit. 



The (Economy of various aquatic plants throws 

 great light upon the subject before us. Different spe- 

 cies of Potamogefon, Etigl. Bot. t. 168, 297, 376, 

 c., Ruppia maritima, t. 136, and others, float en- 

 tirely under water, often at some considerable depth, 

 till the flowering season arrives, when they rise near 

 the surface, and throw up their flowering spikes above 

 it, sinking afterwards to ripen and sow their seeds at 

 the bottom. Nymphaa alba, t. KiO, is very truly de- 

 scribed by Linnaeus in his Flora Suecica, as closing 

 its flowers in the afternoon and laying them down 

 upon the surface of the water till morning, when it 



