Effects of Frost on Plants. 21 



annual report, we find that the thermometer during the same win- 

 ter, sunk from — 8° to — 30° in those portions of the state where 

 this tree is most abundant. It even extends north to the region of 

 the Saskatchawan, according to Hooker. Andromeda polifolia, 

 which extends from New York quite to the shores of the Arctic sea, 

 was killed in the Society's garden. Clethra alnifolia, which was 

 injured at Sketty by a reduction of temperature to only 15°, bears 

 a much greater cold in New Jersey and New York. On the other 

 hand, Ceratiola ei-icoides, passed the winter uninjured in the So- 

 ciety's garden. Sideroxylon (Bitmelia) lycioides was only slightly 

 injured. Querciis virens, (live oak,) though killed at Claremont 

 at — 12°, was unirjjured in the Society's garden, and at other pla- 

 ces ; and, above all. Illicium Floridanimi was unhurt. Of these, 

 the latter is a native of Florida, Alabama and Louisiana exclu- 

 sively, the very warmest portions of the United States, and none 

 of the others occur north of the low region of North Carolina. 

 The northern limit of Magnolia grandiflora, is North Carolina 

 near the sea coast, where the winters are very mild ; yet in Eng- 

 land it seems to have escaped damage except in one or two in- 

 stances ; while M. glauca, which in its native situations endures 

 the winter even of Massachusetts, was much injured in York- 

 shire, where the cold was not so severe as in London. 



" Not the least interesting of the facts observed during this 

 winter was this, that in those places where the cold was very se- 

 vere, the more plants were exposed the less they suffered, and 

 that on the contrary the more they were sheltered without being 

 actually protected artificially, the more extensively they were in- 

 jured." Of this a great number of instances are given. 



" It is well known that plants in a state of growth suffer more 

 from frost than those which are dormant. * * * This is un- 

 doubtedly owing in a great measure, if not exclusively, to their 

 tissue containing much more fluid when in a growing state than 

 when they are dormant. The more succulent a plant or a part 

 of a plant, the more tender it is under equal circumstances. An 

 oak or an ash, is nearly exhausted of its fluid contents by the 

 leaves before the frost sets in, and, in fact, the fall of those organs 

 in deciduous trees is probably caused in part by the inability of 

 the stem to supply them in autumn with an adequate quantity of 

 fluid food : during the winter, but little water is added to the 

 contents of the stem, until after the severe frosts are past and the 



