EXUDATIONS AND ROTTING. 233 



cases the sweet fluid attracts insects which disperse 

 the spores. 



Honey-dew may also be formed without the 

 agency of fungi or insects, when hot and dry days 

 are followed by cool nights, with a saturated 

 atmosphere, e.g. Caesalpinia, Calliandra and other 

 trees in the tropics, which are called rain trees 

 owing to the numerous drops of fluid which drip 

 from the leaves under the abnormall)- turgescent 

 conditions referred to. 



Cuckoo-spit. The leaves of Willows, Meadow 

 grasses and herbs, etc., are often seen with froth on 

 them, in which is a green insect, ApJiropJiora, 

 which sucks the juices from the tissues and 

 excretes the frothy watery cuckoo-spit from its 

 body. 



Slime-fltix. ^The trunks of trees may some- 

 times 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 



