FOREST WEEDH. 387 



(g) Kind of injury done. 



(h) Eelative amount of injury. 



It is highly interesting to note the changes which take place 

 in the constituents of the soil-covering in a forest according 

 to the species of tree grown, and the degree of density of the 

 cover. 



a. Structure of Stem. 



Weeds may be either woody or herbaceous. To the former 

 class belong broom, heather, bilberry, hawthorn, blackthorn, 

 brambles, elder, etc. : to the latter, willow-herbs, groundsell, 

 belladonna, foxglove, grasses (except bamboos), sedges, reeds, 

 and rushes. 



b. Duration of Life. 



Weeds may be either annuals, biennials, or perennials. 



Most herbaceous plants, except some grasses, are annuals. 

 Mullein (Verbascum) and foxglove are biennials, producing 

 foliage in the first year and flowers and fruit in the second 

 year. This class is, however, rare among forest weeds, and 

 all woody plants and the rootstocks of many herbaceous plants 

 are perennials. 



c. Local Occurrence. 



Forest weeds may be classed as belonging to the plains, to 

 swamps, hills, or mountains. Of these, the flora of swamps 

 and of high mountains are most specialised. 



d. Nature of Soil. 



Weeds may be partial, or restricted to certain soils, or 

 indifferent as to soils. 



The restricted class is divided into plants special to sand, 

 clay, loam, calcareous soil, or to peaty and sour soils. It 

 should, however, be remembered that the plants produced in 

 any locality are affected by the subsoil and surrounding 

 conditions as well as by the surface-soil, so that we must 

 not be surprised if a sandy soil, for instance, occasionally 

 produces plants peculiar to other soils. 



Most forest weeds are indifferent as to soil, and appear on 

 soils differing from one another both physically and chemicalty. 



c c 2 



