Hill: Penobscot Vegetation 375 



pools. These usually become brackish, owing to the addi- 

 tion of salt water from the spray and in consequence sup- 

 port a different sort of vegetation. Characteristic species 

 in such places include forms which are typical of brackish 

 marshes rather than fresh swamps, such as : 



Car ex salina var. Spergularia leiosperma 



kattcgatensis Ranunculus Cymbalaria 



Carex maritima Potentilla pacifica 



Scirpus campestris var. 

 paludosus 



B. SECONDARY FORMATIONS OF THE XERARCH AND 

 MESARCH SERIES 



1. Formations Due to Human Activity 



a. Association-types due to cultivation 



In many places tracts of land, which have been under 

 cultivation at one time or another, are abandoned and al- 

 most immediately these begin to revert to a wild state and 

 a series of successions ensue, which lead to a climax type of 

 vegetation. 



Association-types of fall ore fields 



When a plowed field is abandoned it is overrun the suc- 

 ceeding year by herbaceous species, many of which were 

 present as weeds while the field was under cultivation. These 

 form a dense growth which may persist for several years. 

 Common forms include: 



Polygonum tomentosum Galeopsis Tetrahit var. 

 Polygonum Persicaria bifida 



Spergula arvensis Ambrosia arte misiifolia 



Capsella Bursa-pastoris Chrysanthemum Leucanthe- 

 Raphanus Raphanistrum mum var. pinnatifidum 



Trifolium repens Leontodon autumnalis 



Prunella vulgaris var. Solidago nemoralis 

 lanceolata 



