FRANCIS WILLUGHBY. 
81 
In the spring of the year 1669, Mr Willughby 
and Mr Ray entered upon a eourse of inquiries 
into the theory of vegetation. They first de- 
voted .their attention to the motion of the sap 
in trees; the results of their inquiries were 
communicated to the Royal Society, and appeared 
soon afterwards in the Philosophical Transac- 
tions. The probable reason why they did so 
was, the discovery of the circulation of the blood 
in animals, published only about forty years before 
by Dr Harvey, although he had for some years 
tawght the doctrine in his lectures to his pupils. 
They perhaps expected to find something equi- 
valent in the constitution of plants. 
The experiments made at that early period of 
the investigation may be perused with interest. 
It was considered that the following facts were 
established : — “ That the sap of any tree, running 
down the side of it, or dropping on one place, will 
precipitate a kind of white coagulum or jelly ; 
and this, it was imagined, might be the part 
which every year, between bark and tree, turns 
to wood, and of which the leaves and fruit are 
made. 
“ That a tree precipitates more when it is just 
ready to put forth leaves, and is about to cease 
dropping, than at its first bleeding : that the sap 
ascends, not only between the bark and the. tree, 
but by all the pores of the wood. This was 
thought to be undeniably proved by boring in 
the same tree, just before the expansion of the 
leaves, holes of different depths, or the same hole 
F 
