11 



constantly spreading the area of special forms of plant 

 life. When the seed finds a suitable environment, it 

 develops, and the plant multiplies oftentimes with astonish- 

 ing rapidity. Within a hundred years every trace of its 

 foreign origin may disappear. 



Very many species, too, have been introduced through 

 the indirect agency of man. The highways and byways 

 mark the line of march of an invading army. Middlesex 

 county has also long been a manufacturing centre, and 

 about the cotton and more especially the woollen mills, a 

 strange flora is striving to adapt itself to new climatic 

 conditions. Some of these immigrants have undoubtedly 

 come to stay. 



Other plants, directly introduced, have become thor- 

 oughly established, among which may be mentioned the 

 Privet, now common everywhere about Boston. The 

 late Minot Pratt, an enthusiastic botanist, throughout a 

 period of forty years sought to naturalize within the 

 limits of Concord plants from all sections of the United 

 States. Some few of these have disappeared altogether, 

 others maintain a precarious existence, while still others 

 have abundantly increased, in some cases even becoming 

 troublesome weeds. As these plants were skilfully set 

 out in situations to correspond with their natural habitat, 

 they have often been found by occasional collectors, and 

 reported as indigenous. For this reason it has been 

 thought best to incorporate in the present work a complete 

 list of such plants, taken from a manuscript volume 

 left by Mr. Pratt to the Concord Public Library. 



Middlesex county has been fortunate in the location 

 within its limits of the Harvard Botanic Garden, the head- 

 quarters of a corps of able naturalists, and a centre of 

 scientific activity. It has also been fortunate in affording 

 to the botanists of the neighboring city of Boston a con- 

 venient field for exploration. 



