398 



The Museum Gazette 



Oak. 



Retention of leaves by fallen oak branches. This clearly 

 demonstrates that the fall of the leaf in autumn is a vital 

 process. The twig from a fallen branch here exhibited retains 

 its leaves, these have become withered and brown. They are 

 tightly fixed. Note that the leaves have also retained their 



spangle galls. 



Mahonia aquifolium. 



Discoloration of leaves of mahonia the result of injury. 

 These leaves turn a brilliant red colour above all injured parts. 

 They demonstrate very clearly the general principle that 

 changes of colour as well as actual death of parts depend 

 upon interference with the sap circulation, and may be 

 localised by anything which interferes with the mid-rib or 

 veins in which the sap channels run. 



Oak. 



Large oak leaves which have retained their normal green 

 colour until late autumn. They are from shoots which grew 

 from the stool left by the felling of a tree. The tops of the 

 shoots had been cut back in the summer. The explanation of 

 their giantism and freshness is that they have fed in excess. 



MELLEUS GROWING ON A DEAD TREE. 



Let the reader picture to himself an oak tree about as thick 

 as a man's thigh. It is dead, but there is nothing to show this 

 in its bole for the bark looks sound. It is overshadowed by 

 bigger trees which have probably caused its death. There is no 

 trace of injury or decay at its base and no fungus grows there. 

 Higher up, however, at distances of a foot or more from each 

 other there are five or six clumps of a fungus which in its 

 present blackened state of decay (it is December 24) might be 

 taken for a common mushroom, being about that size and 

 having gills. The clumps are as big as fists, ranging from 

 that of a child to those of a man. They are all on the south- 



