72 



Plants with no Apparent Cause for Limited Range. — 

 Excluding plants of the two categories already discussed and 

 taking up plants with no apparent reason for their limited range, 

 it will be found that there are few if any plants endemic to this 

 region, — also that there are still many localized species. The 

 reason for their present distribution is an interesting subject for 

 consideration. 



In the first place it may be pointed out that while both the 

 highland and lowland regions have many localized plants, one 

 and the same species is scarcely ever localized in both regions. 

 Either a localized species of the uplands does not occur in the 

 lowlands, and vice versa, or a species localized in the highlands 

 will be relatively abundant in the lowlands, and vice versa. 



Many species could be taken to illustrate this. A few will 

 suffice : 





Uplands 



Lowlands 



Sagittaria subulata 



none 



rare 



Rhexia virginica 



" 



" 



Jefferso7iia 



rare 



none 



Hydrastis 



•' 



i( 



Eleocharis miitata 



none 



rare 



Jii7icus sjibterminalis 



" 



11 



Solidago lanccolata 



rare 



abundan 



Panicmn clandestinum 



(( 



(( 



Dccodon verticillatus 



<( 



" 



Another interesting thing is the fact -that the localized spe- 

 cies of the highland region occur with few exceptions in 

 wooded uplands while those of the lowlands are confined to the 

 lakes and water courses and their immediate vicinity. Thus 

 Prosartes and Mertcnsia are localized in the highland region and 

 do not occur in the lowlands, while HemicarpJia, DiaiUhera, and 

 Spartina are localized in the lowlands and do not occur in the 

 highlands. 



Looking for the causes for the rarity of these plants, we may at 

 once eliminate climate, as the climate, both as regards temperature 

 and humidity, is practically uniform for both regions. That 

 edaphic factors play an insignificant part seems probable, although 



