VEGETABLE LIFE. 19 



old or new incrassated leaves, acting- like those foliar 

 members of buds called hybernacula. Hence the 

 centre is sufficiently protected from the cold air, and 

 the roots drawing 1 nourishment from a considerable 

 depth in the ground, progress whilst other plants, 

 not similarly situated, are at rest. Besides, these 

 summer sleeping plants may acquire some chemical 

 maturation during their rest, which prepares them for 

 instant action on the return of the temperate season. 



Very differently constituted are trees and shrubs. 

 Their vitality is not local but spread over their whole 

 exterior, and consequently exposed to the depressing- 

 effects of cold air and frost ; so also herbaceous per- 

 ennials having a system of attenuated fibrous roots, 

 and generally near the surface, are kept in cheek by 

 the chilled air. 



Respecting amentaceous plants, as Corylus for 

 instance, there is no ostensible circumstance which 

 can be said to cause the early protrusion of their male 

 and female flowers, more than affects other plants of 

 similar conformation and hardihood. It is true the 

 catkins are mostly formed in the previous summer, 

 and their winter growth is only a relaxive elongation 

 without rigidity of sap vessels or fibres, to endanger 

 the organisation by frost ; indeed flowering, at this 

 dark season, is one of those wise provisions of nature 

 which excites our admiration, for assuredly were 

 such delicate and attenuated bodies exposed to the 

 withering winds and sunshine of the month of March, 

 they would be quickly destroyed before the pollen 

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