112 DR. K. LEDEGANCK ON THE FALL OF LEAVES IN AUTUMN. 



both liquids and gases, seems specially intended to protect the plant 

 against the hurtful influence of the atmosphere. It is produced 

 upon the stripped surfaces of the cortical parts, we have seen it 

 isolate the leaf of which the life is ended, from the bough which 

 remains full of sap and Hfe ; it even shuts off sickly or dying parts 

 of the stem, and its appendages (for instance, unhealthy tubers), so 

 that we may assign to it the term of scarforming, or cicatrising, 

 tissues (tissu vegetal cicatrix). 



When we think of the large number of leaves which adorn the 

 branches of a tree, each of which, falling, leaves a small surface 

 made bare ; when we think of the enormous wound which these 

 little surfaces would make when added together, if they were not 

 already sloughed over when exposed to the air : we may understand 

 how important a part the peridermal tissue has to play for the 

 conservation of the individual plant. It not only prevents an ex- 

 cessive loss of liquids by hindering evaporation at the surface of 

 the wound, but it also preserves it from the hurtful influence of 

 damp and decay. 



Therefore, we can only regard it as an admirable provision of 

 nature that the development of this new tissue, after having 

 served to separate tbe leaf from its support, acts as a pro- 

 tection to the latter during the approaching winter, by preserving 

 it alike from cold, wet, or drought. 



Translator'' s Note. — I have brought these observations of Dr. 

 Ledeganck under the notice of the Quekett Microscopical Club, in 

 the hope that it may prove an incentive to work on this most in- 

 teresting subject. For myself, I hope next autumn to attempt the 

 task, my chief regret being that this memoir came under my 

 notice too recently to permit of observations being made this season 

 which would be trustworthy or useful. 



