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seeds as well as through vegetative means, on the more xerophytic 

 soils. 



With these characteristics in mind, consideration can now be 

 given to the different lines of succession that are theoretically pos- 

 sible between the associations of the three provinces. The possible 

 successions are indicated below, and will be taken up in corresponding 

 order. 



Prairie 



conifer forest 

 deciduous forest 



Conifer forest 



Deciduous forest 



prairie 



•deciduous forest 

 :> prairie 

 ^conifer forest 



As this region is nominally placed in the prairie on maps of vegeta- 

 tion (by Pound and Clements, Engler, Transeau, Sargent, and others), 

 the successional relationships of the prairie will be taken up first. In 

 this region the prairie should not be replaced by the conifer forest, as 

 it is south of the natural range of that province. Locally, where 

 the prairie sod has been accidentally broken, young pines are occa- 

 sionally found, but as the occurrence is so plainly accidental, and tak- 

 ing into consideration other facts of the region, it is perfectly justi- 

 fiable to say that in this region the prairie will never be succeeded 

 by conifer forest. 



In the case of the deciduous forest, matters are different. Prairie 

 and deciduous forest are everywhere in juxtaposition, which results 

 in the shading of the edges of the prairie. This occasions the grad- 

 ual breaking up of the normally dense prairie growth, permitting the 

 occurrence of open places in which the deciduous forest can readily 

 take hold. Such succession is very slow. Occasionally an oak will 

 effect ecesis in the body of the prairie itself — the result of accidental 

 planting, probably by crows or jays. Once started, nothing but acci- 

 dent prevents the development of mature trees, which by their in- 

 creasing shade modify the prairie radially and serve as a nucleus for 

 the spread of the forest. As long as the prairie sod remains intact, 

 however, this succession can not take place. Yet, notwithstanding 

 the fact that things are changing slowly, it is apparent that, under 



