FLOWERS OF THE LAKES, RIVERS, DITCHES, 

 AND WET PLACES 



The vegetation of the land is of one type, that of the water of 

 another. This physical distinction, indeed, has a marked influence 

 upon the forms of plants. Those that grow in water are aquatic or 

 Hydrophytes. While land plants are directly exposed to the air, water 

 plants are not, and the air dissolved in water sometimes contains a 

 larger proportion of oxygen and carbon dio.xide than has atmospheric 

 air. This is important, because plants respire by aid of the former and 

 assimilate by aid of the latter under the action of light upon the 

 chlorophyll, manufacturing their carbohydrates by its means. Ob- 

 viously some waters contain more or less oxygen than others, and 

 some stagnant waters are devoid of any aerating agent. 



The influence of water upon light, also essential to plants containing 

 chlorojjhyll, is great. This influence is least in clear, greatest in dirty 

 water. Depth here is of importance, and is connected with the absorp- 

 tion of different rays of light, red rays being absorbed at the surface, 

 ultra-violet in the lower layers. Water is more uniform in temperature 

 than a land surface, Init the different de[3ths of water have different 

 temperatures, hence the zonal distribution as in the case of light. 



The constituent salts and nature of water have a great influence 

 on the flora of an aquatic formation. This, again, is dependent on the 

 basin which is drained or the soil of the bed. Some water has lime- 

 salts in solution, the carbonic aciil in water dissolving the calcium 

 carbonate, and .so on. Then, lastly, the movement of water is a great 

 factor in deciding its constituent flora. For some plants are floating, 

 some submerged or attached, and some are attached to rock, some to 

 a soil. If water is in a state of rapid motion it abounds in oxygen, 

 if slowly moving it contains less, it still or stagnant still less. It is a 

 means of dispersal of the seeds and the plants, and as the first plants, 



