Of certain animalcules hred on the leaves of the JFillow, and ivhicli 

 prfiduce the knobs or excrejcences frequently J'een on thoj'e leaves. 



X. HERE is a fort of Willow in this country, the leaves of which 

 are of a deeper green, and of a larger fize than others of that tree ; 

 thefe Willows are for the moll part planted for the fake of their 

 young fhoots, which are ufed in hufbandry, and gardening for bind- 

 ing hedges, fences, and branches of trees together, by reafon that 

 they are very flexible, and at the fame time very tough; they are 

 therefore called by us Zeem-teenen, which may be exprefl'ed in 

 Englifh, by the words leathery twigs. 



Upon the leaves of thefe Willows, I have often obferved certain 

 knobs or ritings, and having gathered fome of thofe leaves, and 

 opened the knobs, I at feveral times found that they contained 

 more than one kind of worm or maggot; but none of thofe I at 

 firll faw, appearing to be fiill grown, I opened fome others of the 

 knobs very gently, and, where I faw a maggot inclofed, I flopped 

 up the opening I had made, and put the leaf into a glafs tube, 

 that the animal inclofed might there perfed: its growth, and 

 undergo its change of Itate : this however I did not fee any of 

 them arrive at, though at the fame time, I had obfei-ved many of the 

 knobs vacant, and with a fmall hole in them, through which the 

 maggot had ilTued, leaving the cavity within, partly filled with the 

 excrements it had voided. 



Plate XIV. fg. 8, A B C D E, reprefents one of thefe Willow 

 leaves, on which are feven of the knobs or excrefcences 1 have men- 

 tioned : in fame of thefe a hole is to be feen, as fliewn at the letters 



