568 



extent of the trunk j^ radius; with the appearan-^e of renewed cold in the 

 same year, no resistance has to be overcome in re-opening the clefts, and 

 the following winter only enough to overcome the newly formed wound 

 cover. 



The frost clefts produced in winter, usuall}- extend deep into the inner 

 part of the trunk. The tree is unable to form a new cicatrization mem- 

 brane in the older wood and, conse(|uently, each frost cleft rei)resents a 

 persistent, outwardl)- covered o\er but inwardly unhealed wound This 

 becomes the more significant the more some lateral tangential clefts are 

 added to the radial, large frost cleft. These tangential clefts usually extend 

 into the layers of the spring wood and may be connected with one another b)- 

 radial cross tears. There then occurs an intersected splitting which makes 

 the wood absolutely of no practical use and hastens the death of the tree 

 by facilitating the spread of wood-destroying fungi. 



We thus obtain such structures as are shown in I'ig. 123, wliich repre- 

 sents a cross-section tlirough an oak trunk which, infectecl by rolyponis 

 siilfnrcus from a wound in the branch, has become cleft. 



While the splitting of the trunk, due to long clefts, transversing the 

 greater part of the tree shaft' has often been described, the production of 

 shorter, shallower clefts, which are more easily closed, has not been suffi- 

 ciently investigated. R. Hartig- considered them in the white fir where 

 they are often very shallow, appear in the upper parts of the shaft and 

 usually coalesce very soon without forming frost ridges. Also, thev follow 

 the direction of the wood fibres, i. e., usually somewhat at an angle. P.e- 

 sides occurring in the fir, I find this kind of short frost clefts often with a 

 lip-like v/all in the red beech, tlie cherry and the plane tree. Curiously 

 enough, these varieties are distinguished by a bark which remains smooth 

 for a long time. In this, the preference for certain sides of the tree, in 

 the production of frost clefts, is most easily perceived. If the trees are 

 not accidentally protected by adjacent ones but stand free it is possible in 

 the majority of cases to determine that the west and southwest sides display 

 the most abundant injury from frost. Street plantations of plane til'es. 

 for example, show how differently the different sides of the trees beha\e. 

 At the time when the well-known, normal dropping of the bark scales from 

 the trunk begins, it will be found that most of them are thrown off first on 

 the southwest side of the trunk. 



At times "tears due to druiKjht" are described as frost tears. X()rd- 

 linger''' has called especial attention to this. Tears due to drought, which 

 occur especially in strong trees growing on an impervious soil layer, or 

 undergoing a sudden great scarcity of water, are characterized by repeated 



1 Giippeit, tjber die Folgen iiusserer Verletzungen der Biiume, p. 30, Breslau, 

 1873. He found frost tears in 76 different varieties of trees. 



- Hartig-,, R., Lehr))uch der Pflanzentirankheiten, 3d edition, p. 214, Berlin, 1900, 

 Julius Springer. 



y Nurdlinger, Trockenrisse (falsche Frostrisse) an der Fichte. Auch eiu Oiiind 

 der Rotfaule. Centralbl. f. d. gesamte Forstwesen. Wein 1S78, Part 6. 



