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the county, are in the herbarmm of the Peabody Academy of Science. 

 It is a small, thorny tree. 



Prunus maritima, Wang. (Beach Plum.) This shrub is very 

 abundant at Plum Island, and also along the stone walls at the road- 

 side for some distance into the interior of the county. It is said that 

 the farmers going to the island for "thatch" (Spartina stricta), collect 

 plums and eating them on their way home, throw the stones by the 

 wall, thus establishing the species in the interior towns. 



Prunus spinosa, L. (Sloe. Black Thorn.) Reported as intro- 

 duced in one or two instances. 



Prunus pumila, X. (Dwarf Cherry.) Reported from Andover, 

 by Mrs. A. S. Downs and Rev. H. P. Nichols. It was also collected 

 at Lynn, by Dr. Chas. Pickering, about 1823. 



Prunus Pennsylvanica, L. (Wild Red Cherry.) This is a 

 very small tree, quite common in the county. 



Prunus Virginiana, L. (Choke Cherry.) A tall shrub, very 

 common in all parts. 



Prunus serotina, Ehrhart. (Wild Black Cherry.) The late Dr. 

 Chas. Pickering did not consider this tree to be a native of Essex 

 County, but that it was introduced at an early date by the colonists. 

 The Black Cherry is now very abundant along walls, in fields, and 

 by streams. The trees of this species attain considerable size ; one 

 in Boxford measured by Mr. Sears, in 1875, was, 



Circumference 10 feet at 2| feet from ground. 



U 8 U U Q U 



Height about 60 feet. 



Another, measured in 1879, was 8 feet in circumference 4 feet from 

 the ground. The wood of this tree is very valuable, and it is unfortu- 

 nate that the tree should meet with so much abuse on acconnt of its 

 being the favorite of the caterpillars. 



P. (Amygdalus) nana (Flowering Almond), P. (A.) Persica 

 (Peach), P. armeniaca (Apricot), and P. domestica (Garden 

 Cherry), are all common in cultivation, mostly having been intro- 

 duced at an early date. 



Spiroea opulifoUa,. L. (Nine-Bark.) Probably not a native of 

 the county, although common in cultivation. Mr. C. E. Faxon has 

 found this species undoubtedly indigenous at Blue Hill, Milton, Mass. 



Spiraea salicifolia, L. (Meadow Sweet), forms quite a stem at 

 times, as does 



Spiraea tomentosa, L. (Hardback.) Both are very common. 

 Other foreign shrubby species are met with in cultivation. 



Potentilla fruticosa, L. (Shrubby Cinque-foil.) In Ipswich 

 this remarkable Potentilla is quite common, and it is found in a few 



