310 INTRODUCTION TO BOTANY 
the early spring growth of new parts of the plant or in re- 
plenishing old parts, or may even be retained until another 
year. The passage of sugar-laden sap is through the youngest 
fibrovascular bundles. By boring a hole through the dead 
bark into this region, sap may be withdrawn. When it is se- 
cured in sufficiently large quantities, the water may be evap- 
orated from it until thick sirup or sugar remains. Ordinarily 
Fic. 233. Sugar-maple trees which have been tapped every year for over 
eighty years 
The trees are tapped by boring into them so as to reach the sapwood; then a tubu- 
lar spile is driven into the hole, and a bucket is suspended upon a hook on the 
spile. In this way the sap is caught in the bucket 
a good sugar-maple tree produces 15 or 20 gallons of sap 
in one season, though this amount may be greatly exceeded 
by especially good trees. The percentage of sugar in the sap 
varies widely in different seasons and between different trees 
in the same season, but usually it is from 2 to 3 per cent. 
Individual trees produce in one season from half a pound to 7 
or 8 pounds of sugar. Maple sirup is the partially evaporated 
