FROZEN PLANT-ORGANS. V.)7 



As regards extreme winter-cold the following somewhat 

 different scale applies : — 



i. Very Fikjst-tendku Si-ecies. 

 Sweet chestnut, plane, walnut, many fruit trees, such as 

 apricot, peach, quince and cherry.* 



ii. SOMF.WII.VT Fko.ST-TKN'UEU Si'EclKS. 



Pedunculate and sessile oaks, ash, elms, beech, rohinia, 

 silver-fir, yew. 



Frost- hard ij Spcrios. 



Maj^les, horse-chestnut, lime, poplars, willows, hornbeam, 

 birch, alders, Pi/riis sp., hazel; spruce, Scots, AVeymouth, 

 Mountain and Cembran pines, larch, juniper. 



Pyramidal poplar is the least hardy of the poplars, rowan 

 least hardy of the Pyrus sp. The Weymouth pine may send 

 out second shoots in summer, which are usually killed in 

 autumn or winter. 



.As regards the susceptibility of exotic trees that have been 

 introduced into Central Europe, the following experience has 

 been gained in Germany : — 



A. Susceptibility of Exotic Trees to Late and Early Frost. 



i. VeUY FUOST-TENUEII Sl'ECIES. 



Black walnut, all hickories, Turkey oak ; Abies Nordman- 

 fiicuia, Spach. (Caucasus), Douglas fir, Jeffrey's pine, Pinus 

 poiuIiTosa, Laws. 



Black walnut is slightly less susceptible than common 

 walnut. Carya amara, Nutt, is the hardiest hickory. Nord- 

 mann's fir, sprouting late, is less susceptible than common 

 silver-fir. 



ii. Fkost-tenuek Species. 



American ash, grey walnut {Juglans cineren, L.), sugar maple, 

 Californian maple {A. circinatum, Pursh.) ; Sitka (or Menzies) 

 spruce, Corsican pine, Japanese larch. 



• Apricots and peach trees are killed by 2G° — 3U° C, walnut by 'Mf — 32° C, 

 tlie cheiry-tVL'e by 31° :?'2° C. 



F.P. K K 



