406 Dixon and Joly. — - The Path of 
hension of a greasy substance entering the water-saturated 
wall than a substance miscible in the water such as gelatine, 
and which, even if entering the wall in minute quantities, 
might be very injurious. Its extreme dilution with the 
material of the wall might render its detection by the micro- 
scope impossible. 
We made experiments to test this last possibility. We 
only quote some of these. We may observe, however, that 
all our results agreed in showing the passage of dilute warm 
gelatine from cell to cell — possibly taking place in some cases 
only through the closing membranes of the pits, and conse- 
quently possibly altering the capa- 
bility of the wall for transmitting 
water. 
A length of io cm. straight 
and free from side branches was 
cut from a branch of Taxus haccata , 
the mean diameter being 2-5 cm. 
This was deprived of its bark and 
affixed by an india-rubber ring at 
one end to a glass tube communi- 
cating with an air-pump ; a little 
water in the tube covered the upper 
end of the wood. Woodcut 3 shows 
the arrangements.) On exhaust- 
ing the tube, bubbles rose from 
the surface of the wood. These 
could be stopped by simply im- 
mersing the lower end in mercury. Hence it is to be con- 
cluded that continuous air-passages exist in this piece of wood 
which must be stopped before any tests can be made as to its 
permeability by gelatine. Accordingly the lower end was 
dipped in melted paraffin at about 70° C, the melting-point of 
the paraffin being 56 0 , and the whole length of the stick jacketed 
by water which was maintained at 70° for 45 minutes, a vacuum 
being preserved in the tube attached to its upper end during 
this time. Finally the stick was cooled slowly from above 
