62 ll.OWKRS Ol I.AKl.S, RIXl'.RS, ETC. 



like the first animals, undoubteclK' arose troni a liquid solution, plants 

 have been largely spread o\(r the earth In' water. 



There are certain plants like llydrocliaris, giving its name to this 

 type of flora, which tloat on the surface, unattached, in fresh water, 

 swamp-plants, in still water, .sailing about, and with erect stems and 

 Ieave.s. Here, besides Frogbit, we nia\- furiher include Bladderwort, 

 Duckweed, &c., and Water X'iolet. These plants ha\e the same 

 specific gravity as the water. 



The shoots have lono- iniernudes, thin stems, stalkless or stalked 

 leaves, with threadlike segments, as in Bladclerwort and Water Violet, 

 when submerged. Floating leaves are shield-shaped, egg-shaped, 

 heart-shaped, as in Hydi-ocliaris, Leinna, and the dixision is well 

 shown in different types of Water Buttercup which liave both types 

 of leaves. The plant is secured by its root. Nutriment is largely 

 absorbed by the stem and Ieave.s. 



Many plants growing in water reproduce by division vegetatively, 

 as Frogbit and Duckweed. The pollination of the Frogbit, Water 

 Violet, and Bladderwort is effected by insects, and the Hornwort opens 

 its flowers under water. Frogbit and others are perennial, and survive 

 the winter by forming winter-buds or hibernaciila. which sink in the 

 autumn and rise again in the spring. 



The plants that grow on the loose soil of aquatic formations where 

 the soil is quartz-sand are difterentiated by the movement and salinity 

 of the water, and chiefly flowering plants grow upon it. The roots are 

 chiefly attachments, and the Mare's Tail has few or no root hairs, nor 

 has the W^ater \'iolet. Zostcra forms meadows on account of its long, 

 creeping" rhizomes or underground stems in purely saline waters, form- 

 ing maritime vegetation. Most maritime aquatic plants are Alga;. 



Belonging to what is called the Enhalid formation are the colonies 

 of Zostera growing in salt water, and with /Ya/as, unique amongst the 

 flowering plants, Ruppia and Zainiichellia are found in brackish 

 water. In Zoslcrcx the leaves arc ribbon-like and long, and the roots 

 rhizome-like. Along some shores it forms a regular zone. In brackish 

 water Chara, Water Buttercup, Potamooeton, and MvriopJiylliii]i grow. 



The chief aciuatic lt)rmations of flowering plants are known as the 

 Liiniuca formation, so called from the prevalence of the fresh-water 

 pond snail in it, and are submerged or have floating leaves. The chief 

 types belong to the Pondweed, Water Pepper, Bur-reed, \\'ater Lilies, 

 Water Buttercup, Starwort, Water Celery, &c. The Hydrophytes 

 altogether number some 700, of which we describe 41, and of the 

 Hydrophytes some 120 are lacustral. Here we include littoral, of 



