174 
Some account of Amici’s Discoveries 
former situation, the original motion will also be renewed, pro- 
vided the plant has not been essentially injured in that place, or 
the forced situation has not been too long maintained. The 
circulation will also continue in the one half of the tract, after 
the other has been cut off above the ligature. 
If one of the vessels be cut through right across, the sap 
which it contains will not immediately and entirely "flow out, 
but only that of the one half, — the stream, namely, which is 
flowing towards the cut, — while the other continues its course. 
Vinegar deadens the motion, and even prevents the flowing of 
the sap out of a divided vessel. 
The vessels are formed of an exceedingly delicate, smooth, 
white, transparent membrane, with regular, parallel, greenish 
stripes, running in a perpendicular or spiral direction, according 
to the direction in which the sap circulates. Between the 
stripes of each half of the vessel, that is, between the two 
streams which run up and down, there is always a smooth inter- 
val of the membrane without stripes, of the breadth of five or 
six, or more stripes. Of these smooth intervals there are two in 
each vessel, exactly opposite to each other, and of equal breadth ; 
and, between them, the stripes (which, so far as the vessel is 
perfectly cylindrical, are divided by the intervals into two equal 
semicircles) are equally distributed. 
, These stripeless intervals, which exactly intersect the diame- 
ter of the circle of the cylindrical vessel, form, as it were, the 
partition between the two streams ; and here there is indeed no 
motion of the sap globules, or, at most, a very sluggish and inter- 
rupted circulation. These stripes, of which above an hundred 
may be counted in both semicircles of the vessel, are raised and 
fastened to the internal part of the membrane, and of different 
compactness and strength. Wherever they appear most com- 
pact, thickest, and strongest, and generally in that neighbour- 
hood, and consequently towards the sides of the vessel, we shall 
always remark the strongest and most rapid motion of the sap 
globules. These stripes, therefore, have an evident influence 
on the mode and degree of the circulation. 
When magnified 207,025 times these stripes appear to be 
* 455 times, according to the usual mode of reckoning : Amici gives the mag- 
nified superficies, and 455 =: i»/207,025 — Ed. 1 
