loo REPORT OF NEW JERSEY STATE MUSEUM. 



seeds into the heart of the region, but they seldom establish 

 themselves except when cultivated tracts give them the oppor- 

 tunity. Even along the railroads they seldom spread beyond the 

 artificial road-bed, and when broad, close-cropped clearings are 

 maintained on each side of the track as a guard against fire, and 

 weeds do become established there, they are soon exterminated 

 when the native vegetation is allowed to assume a normal growth. 

 Cultivation not only opens the way for the introduction of 

 foreign plants brought unintentionally by man to whatever 

 country he goes, just like the various animal pests, but it tends 

 to develop weeds out of a portion of the native vegetation. 

 Most native plants are exterminated immediately or in a short 

 time after cultivation, but others seem to find ideal conditions in 

 the altered environment and become quite as much weeds as the 

 foreign introductions. Such species as Polygonum pennsyl- 

 vanicum, P. asviculare, Brigeron annuus, B. ramosus, Leptilon 

 canaAense, Oenothera biennis, Lobelia inflata, Ambrosia arte- 

 misicefolia, Tridens Havus, etc., etc., are known to be native, but 

 all trace of their original range has been lost. 



In New Jersey certain species native of the Middle district have 

 become weeds, notably Linaria canadensis, Oenothera sinuata, 

 Monarda punctata, etc., and these plants seem to take hold in the 

 Pine Barren clearings more abundantly than the foreign weeds. 

 In the Pine Barren bogs the flooding incidental to cranberry 

 growing is quite as detrimental to the native flora as the clear- 

 ing and plowing of the forest. Many of the orchids, Abama, 

 ToUeldia, and other bog species are exterminated, but curiously 

 enough Gyrotheca tinctoria becomes a most troublesome weed, 

 increasing enormously in all cultivated bogs where it may be 

 present, and Amphicarpon a/mphicarpon swarms over the recently 

 erected sand dykes like a veritable weed of long standing. 



Dr. Arthur Hollick has spoken of the Middle district as the 

 "Tension Belt," but it seems to me the real tension belt is in 

 cleared areas in the Pine Barrens where native and introduced 

 weeds and certain Middle district plants have managed to get a 

 foothold and maintain themselves as long as cultivation con- 

 tinues. When this ceases then the native flora asserts itself and 

 seems generally able to re-establish its supremacy and extermi- 



