Slime-flux. - The trunks of trees may sometimes be observed to pour out a slimy fluid from cracks in the bark, or from old wounds, or branch scars. In some cases, e.g. in Oaks, the slime has a beery odour and white colour, and abounds in yeasts and other fungi to the fermentative activity of which the odour and frothiness are due. In other cases the slime is red e.g. - Hornbeam; or brown - e.g. Apple and Elm; or black - e.g. Beech, the colour in such cases being due to the mixture of yeasts, bacteria, and fungi with which these slimes abound. The phenomenon appears to be due to the exudation of large quantities of sap under pressure - root pressure - and is primarily a normal phenomenon comparable to the bleeding of cut trees in spring: the fungi, etc., are doubtless saprophytes, but their activity is concerned with the putrefactive processes going on in the diseased wood, and which may lead to rotting of the timber.
The origin of the wounds in the bark and cortex, and which extend into the wood and other tissues as the putrefactive and fermentative processes increase, appears to be in some cases at least due to lightning.