Secretion -1 

We have already studied secretion due to Epidermis which is an external tissue. Now we will also consider internal secretory structures.

Brazilian Oil Tree
Copaifera officinalis
Young BAZOT Stem Cross-Section Stained with Sudan IV. The circular areas which have stained red contain oil.

Cross-Section of a Secretory Canal from BAZOT. Note the Epithelial cells which line the central lumen of the canal.

The Brazilian Oil Tree (BAOZT) produces volatile oils in almost every place including its fruits and seeds. Oil from the trunk can supposedly be used to run autos.
During one of the Arab oil embargoes there was a lot of interest in plants like these. This tree was growing on the campus of the University of Puerto Rico, Rio Piedras. Somebody in the past had to get the idea to acquire this tree and actually go out and plant it. Many years later I was able to use it in my research, and I got a grant for this purpose. Such events are taken for granted but are not happening now. One of the great aspects of Universities is that thoughtful people do thoughtful things which benefit future generations. We seem to live in an age that can only see as far ahead as tomorrow. Tree planting and other long-term projects simply do not have any support. This needs to change so that future generations will be surrounded by a legacy of thought and concern for tomorrow and beyond.

The Lumen of the duct is surrounded by Epithelial tissue which actively secretes oil into the lumen. The Epithelium is typically one cell layer thick.

Paradermal section of BAZOT Leaf stained with Sudan IV.

Paradermal section through the leaf of BAZOT - The orange spheres are oil contained within Secretory Cavities in the leaf. Secretory Cavities are round to elliptical and traverse a short distance within the organ.