46 THE AMERICAN MONTHLY [Feb., 



Compositae and is closely related to tlie Thoroughworts. 

 Attention was first attracted by the peculiar appearance 

 presented by these roots in summer and autumn. They 

 grow in mud and water and, at the above mentioned sea- 

 sons, produce an extraordinarily extensive root-system. 

 Many of the aquatic roots have an unmistakable tendency 

 to grow up to the surface of the water ; the roots, grow- 

 ing in mud or even transplanted into a dry place, still 

 show a tendency to grow upward. 



The plants studied grew along the shores of the Oswego 

 river in northern New York. It is associated there with 

 Decodon verticillatus, the water-loving Polygonums, and 

 other shore plants over which it grows in great profuse- 

 ness. Its clusters of flesh-colored flowers are produced 

 in August and September. 



A careful study of the structure of the root and also of 

 the literature bearing upon the subject leads to the con- 

 clusion that the function of these roots is to aerate the 

 submerged parts of the plant. 



If respiration be one of the primary functions of or- 

 ganisms and no one will assert that it is not, it is to be 

 expected that modifications to increase the facility and 

 certainty of its accomplishment will be found among the 

 more highly organized plants. The modification of or- 

 gans to secure the best conditions for aeration is the di- 

 rect result of an evolution of forms best adapted to live. 

 Indeed one might justly say that respiration is the first 

 of the functions. The first signs of germination in a 

 seed is the enlargement of air-containing sjiaces between 

 the cells. In some cases these spaces become compar- 

 itively large before active cell division begins. During 

 the succeeding life of the plant, where the massiveuess of 

 tissue or the lack of aeration in the surrounding medium 

 makes it advantageous, provision is made for aeration 

 either by intercellular spaces without any regular organ- 

 ization of tissues, or by a special tissue organized to in- 



