Ronald Lanner's Tree World

What is Sap?

Sap is a water solution that moves through the tree, carrying dissolved substances from place to place. Sap travels in the sapwood, the most recently formed wood, which is just beneath the bark. Its water comes from the soil,and it contains dissolved soil minerals which are translocated into the parts of the tree where they are needed for metabolic purposes. This is often called xylem sap (xylem=wood). It is the water in xylem sap that is transpired from leaves into the atmosphere. Phloem sap travels in the inner bark or phloem of the tree. It consists mainly of water "borrowed" from the xylem sap, containing dissolved sugars that were formed by photosynthesis in the leaves. It generally moves down the tree, and the sugar solution is shunted into the numerous parts of the tree where it is needed for structural or metabolic purposes. Both types of sap can also carry dissolved gases, hormones, vitamins, and amino acids. Sap is indeed the life-blood of the tree. It should not be confused with resins or gums, that are manufactured in the tree as defensive compounds, and which are generally aromatic and sticky.


This site is devoted to trees. Among naturalists, biologists, environmentalists, and others trees get lots of lip service but mighty little respect. Everybody admits to liking trees, but few bother to really learn much about them -- and true respect demands a reasonable level of knowledge. Why is this? Maybe because botanically inclined people spend most of their field time looking down, while to see trees you have to look up. A sniff of wildflowers takes just a quick crouch, but to inhale the spirits of a tall forest tree you are going to have to climb and shimmy, and most of us are decidedly not up to that. Maybe it's because trees are so big, and so much of their interesting parts and activities are found beyond our reach, way up there in those crowns. Or perhaps it is simply because our own faulty anatomy has dictated weak little necks that start to hurt almost immediately we turn our heads up to see what that little bird is finding in that oversized tree. As they say -- whatever. But my years of chasing down firs, sticking pins in pine shoots, putting bags on acacias and larches, and snipping off foliage of potential hybrid pines persuades me that getting the average nature freak to learn something authentic about a tree is simply much harder than doing so with the world's minor plants.

Therefore I offer this site to focus on trees in a way that departs from my many years of teaching university forestry students. This will be a personal approach. I will post on it information about my tree books -- there are six so far-- and I'll offer them for sale. If space permits, I'll also offer for sale books from my collection and duplicates. And I may also offer old prints of trees: lithographs, etchings, engravings, etc., distinctive enough to warrant hanging in your office or den.

Finally, I will publish commentary about trees that reflect my opinions, theories, and crotchets, including abstracts of recent articles I have written. These will appear on the DISCUSSION page.If you wish to make comments to me, email at

Finally a book on the bristlecone and foxtail pines with a scientific view of tree longevity
The first natural history of the bristlecone and foxtail pines of the western United States, written for the outdoor and plant enthusiast who wants to understand these amazing trees that invite us into their mountain homes.
Color illustrated regional tree guide
A guide to all of the cone-bearing trees of California, illustrated with over 135 color photos and 54 full-page water color paintings of the species.
A Co-evolutionary Tale of Pines and Corvids for anyone interested in plants or animals.
The birds bury the seeds and the sprouting trees eventually feed the descendants of those birds. A Mutualism that enlivens the Rockies, Sierra, Alps, and more.
The Original Fall Colors Guidebook for Leaf-Peepers and Tree Nuts
The science of fall color change in the leaves of our Northeastern hardwood forest with essays on the natural and cultural history of the major trees that contribute to the annual spectacle.
First volume in the Fleischmann Great Basin Natural History Series
The much sought-after, but out-of-print classic on the trees between the Rockies and the Sierra Nevada
A Southwestern classic on the tree that enriched human life on the desert edge
An all inclusive view of the woodland-forming pinon pine, which grows where few other trees can, and whose nutritious nut-like seeds have allowed birds, quadrupeds, and human cultures to thrive in the arid Southwest and Great Basin.

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