Exudations and Rotting.The outward symptoms of many diseases consist in excessive discharges of moisture, often accompanied by bursting of over-turgid cells, and eventually by putrefactive changes.
Lime in hot weather is owing to exudations of sugar.
In many cases the punctures of Aphides and Coccideae are shown to be responsible for such exudations, and at least one instance is known where a FungusClaviceps-causes it.
But it also appears that honeydew may be excreted by ordinary processes of over-turgescence pressing the liquid through water-pores, as in the tropical Caesalpinia, Calliandra, &c. That these exudations on leaves should afterwards serve as pabulum for Fungie.g.
Many species produce gums and resins, their stems being encrusted with the exudations, and pungency and aromatic odour is an almost universal quality of the plants of desert regions.