76 
and they are nothing elfe but the dilatation, 
or more remarkable, yet irregular excrefcences 
of the inmoft and nervous part of the Willow 
leaf. ‘Thefe tubercles, therefore, are properly 
compofed of a collection of the very fine veffels 
of the leaf, which, concreting together into a 
maf{s, form an extuberant little knot ; to which 
the two coats of each fide are fo ftrongly joined, 
that they cannot, but with difficulty, be fepa- 
rated; nay even, thefe too are fo much dilated 
by force of the tubercle, as to lofe their down 
or hairs in that part. 
The external figure of thefe verrucz, or tu- 
bercles, is very irregular: they are fometimes 
roundifh or ovalc, fometimes oblongd, and 
they are wrinkled e, fmooth, and of many other 
furfaces and forms. ‘Their internal ftructure 
confifts, as it were, of little grains, refembling 
broken free-{tone of a large grain, and is filled 
with fmall chinks and corners, vifible only 
with a microfcope.* The outward furface is 
of a (fometimes faint, and fometimes full) green 
colour, and is variegated with purple, red and 
yellow, all together or feverally : there are 
likewife fome rufty, {mall and blackith {pots 
obferved in fome of them, which are like marks 
of vermiculation f. ‘Thefe tubercles are with- 
in of a full green, and at the fame time fome- 
what yellowith here and there : this yellownefs 
probably arifes from hence, that the Worm 
hath confumed the inward fubftance about 
thofe places. 
Thefe warts occupy various -parts of the 
leaf: they are fomietimes found g in the mid- 
dle region, adjacent to the nerve; they lie 4 
fometimes near the extremityof the leaf; fome- 
times they are on the nervez; fometimes more 
{wollen or depreffed, and again are fituated at a 
greater or lefs diftance from each other ; and 
therefore nothing certain or regular can be de- 
termined, in this refpect, about them. They 
are conftantly extuberant beyond the furface of 
the two coats of the leaf: but in that fide of 
the leaf where the nerves run, they clue ee, 
project more than in the inward fide; tho’ 
have found fome which rofe to an equal height 
on each fide & I have likewife feen fome 
which occupied the footftalk of the leaf/; but 
thefe were fewer. 
There is great difference between the warts, 
in regard to bignefs and fmallnefs, and alfo 
with refpect to their greater or lefs number. 
In fome leaves there are feen only one or two, 
in others ten or twelve. They differ alfo great- 
ly in fize. The reafon of which is, that fome 
of them are riper than others ; or they are older, 
or have begun to increafe afrefh. I {hall here- 
after treat of this matter in the hiftory of the 
egg, and {hall then likewife defcribe their hard- 
nefs and tendernefs. : 
“When I opened fome of thofe warts of thefe 
leaves, on the r4th of June, I met with quite 
different things therein. In fome, which were 
Th BOOK of NATURE; 
_poflible. 
Ory * 
fhut very clofe, I found a Vermicle, or Worm, 
like the Caterpillar of the Bindweed, together 
with its excrements, and a caft {kin near it. 
In another, which opened outwardly, with a 
round or orbicular orifice, I found another Ca- 
terpillar, of the fame fhape with the former, 
but confiderably larger. In others that were 
not perforated, and ftill contained. their Ca- 
terpillar of the fame kind within, I ob- 
ferved this was fuffocated, or had been killed, 
by fome other Worms, which likewife lodge 
themfelves in the warts. I obferved that 
the rain had fallen into fome others, that 
had holes, and were deftitute of an inhabitant. 
In others again I found other infects, which 
had caft their eggs there. Nay, I fometimes 
found the little caverns of thefe tubercles occu- 
pied by {mall Spiders, which had fhut up the 
orifice with one of their webs. I thall treat of 
all thefe things more particularly hereafter. 
Thefe differences, obfervable about one and 
the fame kind of tubercle, may, no doubt, 
lead ignorant perfons into error. Indeed, Iam 
firmly perfuaded, that all who apply them- 
felves to experiments will be deceived, unlefs 
they thoroughly inveftigate them, and endea- 
vour to find out their firft principles. Where- 
fore, as I had at different times obferved what 
is before related, I have again, at length, exa- 
mined thefe excrefcences with all the care 
And thus I have, at length, difco- 
vered the real eggs out of which thofe firft Ca- 
terpillars, which I faid I found in the tubercles, 
are produced, At the fame time alfo, I difco- 
vered the reafons why other infects alfo go 
into thefe warts, | . 
On the faid rath of June, I opened a great 
number of tubercles, of all kinds and figures: 
in the fmalleft of them I found real and per- 
fect eggs, fo circumftanced in every refpect, as 
if they had been laid there by the infe@. The 
leaf of the willow, in which I found fuch an 
ege, had but very lately budded, and was ftill 
tender, though it had obtained its full fize and 
form. I found in this leaf the rudiments of 
feven {uch excrefcences, which I reprefent in 
each fide of it, Tab. XLIV. Fig. 1.7. Some 
of thefe were a little larger, others {maller ; 
but the minuteft of them were fo fmall, that 
they could be obferved only by reafon of the 
{mall change which was obferved in the colour 
of the leaf. The largeft of the tubercles, 
which began to {well a little, were of a yel- 
lowifh green colour; but the {malleft of all, 
which did not yet project beyond the furface 
of the coats of the leaf, was diftinguithed from 
the leaf itfelf only by a paler yellow colour, 
We mutt here obferve, that the egg was alfo 
fmaller in the fmalleft than in the largeft ex. 
crefcences; in which I conftantly found it 
much larger, and more advanced and forward, 
This egg was of an oblong figure, Fig. 11. 7, 
without any rings, having one end thicker, 
‘* Thefe tubercles and warts, like galls, and the tufts on the dog-rofe, all arife from the punctures of infeéts; and as there are 
many kinds of thefe infects, it is not ftrange that the tubercles are of various forms. ‘They are all produced by wounds, at which 
the eggs of the parent-animal are introduced ; and the young Worm conitantly appears within them. ‘Thefe Worms are, in genes 
yal, very weak and 
4 
defencelefs; and this feeras a provifion of mature to hidg them from theis enemies: 
the 
