New Yoek Ageicultural Experiment Station. 29Y 



During the cold weather of January and February, 1855, numerous 

 low-temperature clefts in trees in and around Berlin reopened, and 

 Caspary^ made a study of the forces concerned in their production. 



Early winter had been mild and rainy, but about the middle of 

 January severe cold weather began and the temperature continued 

 below freezing with an occasional freezing rain, until the latter part 

 of February. Measurements of many trees and their clefts were 

 made and the wind and weather records were closely followed 

 through the cold period. 



Caspary concluded that clefts in tree trunks occur without refer- 

 ence to the points of the compass and that Goppert's view concerning 

 the relation of the wind as a causal factor can therefore not be correct. 

 He observed, however, that only trees along roads and about the edge 

 of forests are cleft while those in the interior of forests were not cleft. 



Since it had been showm by others that after ice is once formed it 

 contracts on a further lowering of the temperature, Caspary main- 

 tained that clefts occur in tree trunlvs as a result of the contraction 

 of the wood, and not because of expansion resulting from ice forma- 

 tion in their interior as many believed. If clefts were formed owing 

 to expansion resulting from ice formation they would close again 

 when the temperature sinl^s below the freezing point of tree-trunks 

 because ice has a very high coefficient of contraction, but as a matter 

 of fact they open wider. 



In a final summary he states that clefts result in introduced annual 

 plants and shrubs during the first severe frost of a season, and that 

 they are caused by the expansion of the abundant sap while freezing, 

 especially in the cambial region; and that such clefts may occur on per- 

 fectly normal plants. However, in native trees clefts occur at lower 

 temperatures and are said to be chiefly due to the excessive contrac- 

 tion of the peripheral wood, although in case of large trees in part to 

 the differences in the temperature between the interior and exterior 

 of the trunks. The rupture is said always to occur at the weakest 

 point, determined by the location of decayed parts or wounds. 



According to de Jonghe^ clefts are partially due to sudden changes 

 of temperature in spring which are said to " cause a reflux of the 

 ascending sap," but chiefly to " the sun's rays which cause the burst- 

 ing of the bark a.nd occasion the splitting." He says that the " rents 

 are always on the side next the sun and never on the east, north, or 

 northwest sides." He held also that " In general, sun-strokes are 

 more common on trees growing in a strong, moist soil, than in one 

 that is light and dry." 



In a second article, first published in the Echo de Bruxelles, de 

 Jonghe^ makes some fm'ther additions to his former observations. 



^ R. Casparj\ Ueber Frostspalten. 



Bot. Zeit. 13: 449-62; 473-82; 489-500. 1855. 

 * de Jonghe. Sun strokes. 



Gard. Chron. Agrl. Gaz. 1856:213. 1856. 

 ' de Jonghe. The sun-strokes in pear trees. 



Gard. Chron. Agrl. Gaz. 1856:230. 1856. 



