1006 MINNESOTA BOTANICAL STUDIES. 



SOIL SHORES. 



Of zonal shores of this character, not already discussed, 

 really the only examples are the mud flats and mud banks, 

 which are so rarely developed on Lake of the Woods. All 

 other soil shores are largely azonal. For a soil shore can 

 hardly be maintained, except as morass which has been con- 

 sidered by itself, or as humus or drift, quite outside the sphere 

 of wave-influence. 



Mud flats. Upon these shores the algal pools are promi- 

 nent, and in them commonly Lemnais developed in small quan- 

 tities, so they may properly be denominated Lemna pools. If 

 the mud flat be not inundated too frequently, as is almost uni- 

 formly the case, a few Garices may be established, but in Lake 

 of the Woods, with its considerable variations of water stage, 

 such areas are commonly barren, if they appear at all. Barren 

 mud-flats differ from morasses principally because they are 

 thus barren. Yet on such shores an outward zone of Lemna 

 pools is often backed by an area of Oarices, and the whole con- 

 stitutes a temporary formation easily destroyed whenever the 

 mud is rearranged by the action of the waves. Upon such 

 shores, if they be in proximity to a bed of Nymphaea the pond 

 lilies often creep, and during the summer the edge of the flat 

 may be tenanted by these almost amphibious plants. 



Mud banks. These are always small in extent, and often ap- 

 pear, as the most temporary of formations. Sometimes deltas 

 of mud and silt are deposited upon strand or upon flat rock 

 shores by small temporary streams, and thus a peculiar 

 group of nitrophytic plants will be established upon the strand. 

 In other cases the mud bank is developed from a mud flat, 

 when the ridge is tenanted by Carices, small Ranunculi, Veron- 

 ica, sometimes Scutellaria, and in brief is like the zones estab- 

 lished around pools in the back strand, as previously described. 

 Although nitrogenous, these mud shores are so impermanent 

 that no opportunity for plants of high rank to develop is of- 

 fered. 



Coming to a consideration of azonal shores, and the methods 

 of distribution upon them, it is worth noting that very often 

 little complexity of distribution, at first sight, characterizes 

 these areas. The solid Populus or Beiula formation extending 

 to the water's edge seems homogeneous, and unless it is studied 

 in detail might be mistaken for a true zone. Yet, often such 

 shore floras are quite azonal, and should be regarded rather as 



