n. sapwood; the thin white layer between the bark and wood of a tree
the GNU version of the Collaborative International Dictionary of English
n. The white and softer part of wood, between the inner bark and the hard wood or duramen; sapwood.
The Century Dictionary and Cyclopedia
n. The lighter-colored and softer part of the wood of exogenous plants, between the inner bark and the heart-wood.
Word Usage
"Incisions are made into the alburnum of the seringueiras; below the wound small pots are attached, which twenty-four hours suffice to fill with a milky sap."