100 BERTHA'S VISIT TO HER 



of plants as we saw, last Saturday, had happened 

 to the carrots, that frost kills them ? 



" Perhaps," said he, " that may have some in- 

 jurious effect upon tender plants; but it is by 

 bursting the sap vessels that frost does the most 

 mischief. 3 ' 



" I suppose the sap freezes, and that its ex- 

 pansion bursts the vessels?" I said. 



" Just so," replied my uncle ; (t this frequently 

 occurs, even in moderate frosts, to tender plants, 

 especially if they are succulent. But in very 

 severe winters even forest trees have suffered. 

 In the great frost of 1739 and 1740, the largest 

 branches were split from end to end, and num- 

 bers of the most hardy trees died in conse- 

 quence." 



All this made me very anxious about my 

 garden and my nice plants ; I had already put 

 stable litter on them ; and 1 asked my uncle, 

 if that should be frozen through, what he would 

 recommend me to do. 



He advised me to bend some long withies 

 of sallow over them, so as to leave a small space 

 above the surface of the litter, and over the 

 sallows to spread either a mat or fir boughs ; 

 and he reminded me that he had explained 

 some days ago the use of this process. 



" Besides which," said Mary, " I believe the 

 stillness of the air under the covering helps to 



