525 



It is important to refer here to the behavior of the mineral substances 

 in leaves killed by frost, because we thus obtain an insight into the loss in 

 substance caused by the destruction of the foliage in spring frosts. 



Schroeder's^ analyses of red beech foliage which a May frost had killed 

 and which, four weeks later, was examined in the dried condition, gave the 

 following: In the frozen foliage, the whole nitrogen content (3.56 per 

 cent.) of the fresh May leaves is found, while in the autumnal leaves, only 

 about 1.33 per cent, remains, so that, therefore, almost three times as much 

 nitrogen is lost for the plant from the loss of the May foliage as in that of 

 the autumnal falling of the leaves. The dry substance gives 3.01 per cent, 

 ash. Of this ash, 22 per cent, was phosphoric acid, i. e., as much as fresh 

 May leaves, while the July leaves possess only 5 per cent. In May leaves 

 about 30 per cent, of potassium was present normally ; in frozen ones, how- 

 ever, only 5 per cent. Naturally very little calcium was present in the 

 young foliage (6.78 per cent, in healthy foliage, 4.70 per cent, in frozen 

 foliage) ; while the vegetating July leaves possessed three times as much 

 (20.34 per cent.) the dead November leaves actually exhibited 37.O0 per 

 cent. 



In opposition to the opinion that foliage killed by spring frosts remains 

 hanging on the trees, wdiich thus gives its valuable mineral elements time 

 to wander back into the trunk, reference should be made to Ramann's inves- 

 tigations-. He proved that the foliage of the oak, spruce and fir, killed by 

 cold, at first possessed the same composition as fresh foliage, when analyzed 

 before a rain, but, during the rain, it underwent a very considerable change. 

 Ramann found that, within yi hours, water withdrew not less than 19.219 

 per cent, of the whole ash of red beech leaves and actually 26.46 per cent, of 

 the oak. This easy diffusibility of the ash elements should not be considered 

 to be the result of later decomposition, as is proved by the fact that the 

 greater amount had been leached out in the first 24 hours ; viz., in the beech 

 15.42 per cent.; in the oak, 19.66 per cent. These latter amounts gave in 

 pure ash 11. 15 per cent, and of extraction for the trunk, 14.18 per cent, 

 for the oak. 



The amount to which loss of the foliage injures the main body is shown 

 in another difi:'erent work by Schroeder^ on "The migration of nitrogen and 

 mineral elements during the first development of the spring growth." The 

 exhaustion of phosphoric acid in the trunk during the production of the 

 young growth is the greatest, namely, 46 per cent. ; then follows potassium, 

 X2 per cent, of which is used up ; nitrogen and magnesium are removed from 

 the trunk up to possibly 26 per cent. Before the end of this period, 12 per 

 cent, calcium and 84 per cent, of the initial amount of silicic acid are added 

 and replace the loss. Of the whole amount of nitrogen, potassium and 



1 Schroeder. Unter.suchung' erfrorenen Buchenlaubes. Forstchemische u. pflan- 

 zenphysiologische Untersuchungen. Part 1, 1878, Dresden, iJ. 87. 



^ Ramann, Aschenanalysen erfrorener Blatter und Triebe. Bot. Centralbl. 

 1880, p. 1274. 



^ loc. cit. p. 83. 



