SBCT. II. DISEASES. 503 



leaf then becomes reflected and conduplicate, en- 

 closing the eggs with a few reddish protuberances 

 on the upper surface. The embryo is nourished by 

 this fluid ; and the hoariness is converted into a fine 

 cottony down, which for some time envelopes the 

 young fly. 



The leaf of the Lime-tree in particular is liable And 



Lime-tree. 

 to attacks from insects when fully expanded ; and 



hence the gnawed appearance it so often exhibits. 

 The injury seems to be occasioned by some species 

 of puceron depositing its eggs in the parenchyma, 

 generally about the angles that branch off from the 

 midrib. A sort of down is produced, at first green, 

 and afterwards hoary ; sometimes in patches, and 

 sometimes pervading the whole leaf, as in the case 

 of the Vine. Under this covering the egg is 

 hatched ; and then the young insect gnaws and in- 

 jures the leaf, leaving a hole, or scar of a burnt or 

 singed appearance. 



Sometimes the upper surface of the leaf is covered 

 with clusters of wart-like substances somewhat 

 subulate and acute. They seem to be occasioned 

 by means of a puncture made on the under sur- 

 face, on which a number of openings are discover- 

 able, penetrating into the warts which are hollow an4 

 villous within, 



SUBSECTION XI. 



Consumption. From barren or improper soil, Cause? of. 

 unfavourable climate, careless planting, or too fre- 



