NOTE and COMMENT 



Boundaries of our Floras. — As every student of 

 botany is aware, the plant covering of our country may be 

 divided into several distinct floras, and within these floras 

 mav be found several lesser floras whose boundaries are 



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determined by soil, moisture and the like. As an illustra- 

 tion, take a peat bog nestling in some hollow in a glacial 

 moraine. There is scarcely a plant that is common to the 

 two adjoining regions. Each is, as it were, a world to 

 itself. Where moraine and bog flora meet, a single step 

 may carry the observer from one entirely distinct floral 

 region to another quite as distinct. Again, where sand- 

 stone and limestone regions adjoin, the transition from 

 one flora to another is often most marked. In the course 

 of a few miles there may be an almost complete change in 

 the plants. The existence of still greater groups of plants 

 in which these lesser groups are merged is indicated by 

 our botanical manuals which commonly attempt to cover 

 a natural region of this kind. The numerous manuals cov- 

 ering the Northeastern States are good examples. The 

 limits of any of these natural regions is set by conditions 

 of soil, water elevation and latitude much as similar limits 

 are set to the lesser floras, but the greater groups are 

 seldom as distinctly outlined as these latter. Neverthe- 

 less one can say in a general way where one flora leaves 

 off and another begins. Perhaps one may be said to end 

 when less than 25$ of its characteristic species can be 

 found. In a region where more than r>O c /c of the plants 



