Minnesota Plant Life. 453 



The depth at which quondam land plants are able to grow is 

 in some instances very great. Thus Magnin is authority for the 

 statement that one variety of moss was found at a depth of 

 nearly 200 feet in an Alpine lake, showing on the part of an 

 originally terrestrial plant a very high degree of adaptation to 

 the aquatic life. Nothing of this sort is known to occur in 

 Minnesota, and beyond 25 feet only algae and bacteria are 

 likely to be discovered, while into such deep water pondweeds 

 and waterweecls rarely extend. 



Abyssal vegetation and modified hydrophytes. The vari- 

 ous classes of hydrophytes which have been discussed may be 

 grouped under the general name of aquatic vegetation. Some 

 forms of aquatic vegetation are scarcely represented in Minne- 

 sota, for example, hot spring vegetation, the various seaweed 

 classes, and snow 7 vegetation. Those which have been discussed 

 comprise the bulk of Minnesota aquatic species. The class de- 

 scribed by Warming as abyssal vegetation occurs, however, in 

 the deep waters of Minnesota lakes from 50 feet below the 

 surface to greater depth. The darkness is so great in such 

 abysses that green plants scarcely exist, though blue-green algae 

 and diatoms are known to occur at depths from 250 to 300 

 feet, being able to utilize the extremely small amount of light 

 which penetrates to them. Most abyssal forms are bacteria. 

 These occur in the deepest waters, either suspended or in films 

 along the bottom, forming, in such depths, a living slime or ooze, 

 as may be determined by microscopic examination of deep lake 

 soundings. The bacterial vegetation occurs also in moist or- 

 ganic substrata, such as the bodies of animals, where a large 

 percentage of the substance is water. So the parasitic bacteria 

 of disease, either of plants or of animals, might possibly be 

 described as forms of hydrophytic vegetation. The bacteria, 

 too, which live upon decaying organic matter, such as the sul- 

 phur bacteria and the ferment-producing bacteria, may be re- 

 garded as constituting a sort of water-loving vegetation, and, 

 therefore, may be classified here. 



Swamp vegetation. The remainder of the hydrophytic 

 classes may be included under the general term of swamp 

 vegetation. This is the plant group that shows itself typic- 

 ally in swamps, in bogs, in marshes, moors and tundras. 



