Minnesota Plant Life. 13 



jiasses over distinct zones of aqnatic vegetation. First, there 

 V, ill he the sedges at the water's edge, then the reed-grasses, or 

 N\ild rice in a little deeper water, then the bulrushes with their 

 cvlindrical, leafless stems rising from submerged rootstocks 

 below, and exposing as small a surface as possible to the action 

 of the surf. Next will come the pond-lilies and water-lilies, the 

 water-shields, and sometimes the lotus with its circular leaves 

 rising from or floating upon the water and presenting every- 

 where their arched margins to the waves. Then come the pond- 

 weeds and milfoils with their stems and submerged leaves 

 ascending through the water but not reaching the surface, and 

 finally the bass-weeds with their lime-encrusted stems and 

 leaves lying upon the bottom at a depth of from ten to fifteen 

 feet. Whether one climbs a hill, rows out into a lake, walks 

 from the margin of a stream back to the prairie or the woods ; 

 whether one steps from his house and across the road into a 

 field, or strolls from a meadow up to a wooded bank, he will 

 find that he is traversing zones of vegetation. The occasion for 

 such a distribution of plants in zones is to be sought generally 

 in the topography of the region, and where there is great irregu- 

 larity in the topography there is irregularity in the zones, while 

 sometimes over a level no zones appear. Sometimes, also, 

 where the topography is favorable to the development of plant 

 zones special conditions of distribution serve to obliterate them 

 or prevent their occurrence. 



The same general causes which tend to separate the forest 

 from the prairie, defining their limits, are seen to mark also the 

 l)oundary between one portion of the forest and another. Just 

 as the great prairie group of plants strives as a whole to en- 

 croach upon the forest, so the plants at the base of a knoll strive 

 to climb it and establish themselves over its surface, and mean- 

 while quite as vigorously the plants on the knoll attempt to 

 make their way into the gullies and sloughs. The plant on 

 drier soil may be regarded as always endeavoring to accommo- 

 date itself to moister soil, and that on moist soil as always strug- 

 gling to gain a foothold where the moisture is not so 'great. 

 So there are often seen at the margin of ponds the pond-lilies 

 emerging as far as they are able upon the mud, exerting them- 

 selves to the full limit of their structural qualities to maintain 



