128 FOREST PROTECTION 



Absolute cold is not injurious, eo ipso, to native species, which 

 know how to protect themselves 



by leaves dropped 



by non-freezing cell contents 



by lignification 



by cork layers, bud scales, hairs 



by color 



by position (rolled up rhododendron leaves) 



by beginning growth late and by finishing it early. 

 The death of a specimen, or of parts of it, is brought about, in all 

 probability, by a rapid transition from cold to warm (cite 

 various theories, and experiments made to support them). 

 Hence it is that the severe frost of winter, or frost occurring 

 at a time at which plants are protected, is less injurious than 

 a light early frost in fall or a light late frost in spring. 

 Frost occurring unexpectedly is most injurious, — and particularly 

 BO to the young parts of an old plant or to a plant, all parts 

 of which are young and tender (e. g., germinating seedlings). 



(a) Influencing factors are: 



Locality (frost holes), latitude, altitude, exposures 

 (eastern) ; 



Atmospheric conditions preceding and following 

 a cold spell; 



Snow cover; 



Condition of plant (germs sprouting; buds open- 

 ing; shoots lengthening; lignification unfin- 

 ished) ; 



Size (age) of plants; 



Presence or absence of wind. 



(b) Consequences of frost are: 



Failures of nursery beds; 



Failure of natural seed regenerations; 



Failure of seed years; 



Failure of seedlings to compete with weeds (e. g., 

 sedgegrass and walnut at Biltmore), and with 

 rabbits (e. g., maple and chestnutoak at 

 Biltmore); 



Saplings and seedlings growing bushy or forking 

 (cherry, loosing tips of shoots incessantly; 

 larch, at Biltmore, on Bradley Plantation, 

 due to September frost, 1906; echinata at 

 Biltmore, everywhere, due to September frost, 

 1906); 



Aristocrats smothered by mob (walnut at Bilt- 

 more overtopped by hard maple, owing to 

 frost); 



