ABSORPTION OP LEAVES. 157 



the resinous exudation of Lombardy Poplars, Populus 

 dilatata. Ait. Hort. Keiv. v. 3. 406, which he supposes 

 to be the tears of Phaeton's sisters, who were transform- 

 ed into those trees. Such exudations must be consid- 

 ered as effusions of the peculiar secretions ; for it has 

 been observed that Manna may be scraped from the 

 leaves of Fraxinus OrnuSy Fl. Grcec. t. 4, as well as 

 procured by incision from its stem. They are often 

 perhaps a sign of unhealthiness in the plant ; at least 

 such appears to be the nature of one kind of honey-dew, 

 to which the Beech in particular is subject, and which, 

 in consequence of an unfavourable wind, covers its 

 leaves in the form of a sweet exudation, similar in fla- 

 vour to the liquor obtained from its trunk. So likewise 

 the Hop, according to Linnseus, Faun-. Suec. SOS, is af- 

 fected with the honey-dew, and its flowers rendered 

 abortive, in consequence of the attacks of the caterpillar 

 of the Ghost Moth, Phalcena Humuli^ upon its roots. In 

 such case the saccharine exudation must decidedly be 

 of a morbid nature*. That wax is also an exudation 

 from the leaves of plants, appears from the experiments 

 recorded by Dr. Thomson in his Chemistry^ v. 4. 298, 

 and it has been long ago asserted that wax may easily 

 be gathered from the leaves of Rosemary. On this sub- 

 ject I have not made any experiments to satisfy myself. 

 With respect to the absorbing power of leaves, the 

 best observations that have been made are those of Bon 



* I do not mean to dispute the accuracy of Mr. Curtis's excel- 

 lent paper, TV. of Linn. Soc. v. 6, written to prove honey-dew 

 to be the dung of Afihides. I only contend that there are more 

 than, one kind of honev-dew. 



