Lake Maxinkuckee, Physical and Biological Survey 133 



COMPARISON OF AQUATIC AND LAND FLORAS 



Perhaps the most striking difference between the flora of a land 

 and of a water area is that the land flora lies open to the eye while 

 much of the flora of a lake, especially of a deep lake, is hidden 

 from view. It is easy to form a fairly complete mental picture of 

 a landscape with which we are familiar, but in the case of a flora 

 at the bottom of a lake the situation is entirely different. In the 

 case of permanence or persistence of individuals, there are curious 

 differences. On the land, there are herbs, shrubs and trees an- 

 nuals, biennials and perennials the trees conspicuous landmarks 

 enduring year after year, the herbs many of them dying entirely 

 down with the course of a year. On the other hand, the aquatic 

 flora is almost entirely herbaceous; the only analogue we have -to 

 trees being the water-lilies and spatterdocks, the thick horizontal 

 rootstocks of which would, if standing erect, make respectable 

 saplings. But while the plants under water are all herbaceous and 

 relatively frail, the phenomenon of annual growths which live but 

 to produce seed, and perish when that is done, does not obtain 

 among the aquatic plants. The only case that comes to mind is 

 that of some of the delicate Charas and Nitellas, and the slender 

 Naias which grows at the water's edge, and the deeper growing 

 plants of Naias. In a certain sense, at least so far as plant life is 

 concerned, the region under water may be described as sub-tropical. 

 The most important difference between the temperate zone and the 

 tropics is, not only in a greater amount of heat in the tropics, but 

 also in the more equable distribution of the heat throughout the 

 year, and the absence of a freezing temperature at any time ; and 

 this is just what we have in the waters of the lake everywhere 

 below the freezing surface. The temperature of the air about the 

 lake has a range of about 125 F., frequently going considerable 

 below freezing, while the water under the freezing layer at the sur- 

 face has a range of only about 55, or not half as much as that of 

 the air, and is always exempt from a freezing temperature. 



In the region immediately about the lake the lover of beautiful 

 grounds may wish in vain for the "broad-leaved evergreens", the 

 holly, the ivy and the rhododendron, but just a little way beneath 

 the ice the broad green delicate leaves of the pond-weeds retain 

 throughout the coldest winters almost the freshness of summer 

 days. 



Moreover, in the methods of perpetuating their kind, the aquatic 

 plants differ considerably from the land plants in that there is 

 hardly a single species which does not have some effective method 



