Definition of guano. : a fertilizer containing the accumulated excrement of seabirds or bats; broadly : excrement especially of seabirds or bats.
Developmental Biology Online. Epithelial tissues come in three basic types: squamous, cuboidal and columnar. These three types of tissue are seen in either simple (only one cell layer thick) or stratified (many cells in thickness) arrangements.
As a complex tissue, it is composed of four cell types: vessel elements, tracheids, parenchyma cells and fibers. Vessel elements, non-living, barrel-like cells, and tracheids, non-living, tapered cells, are the actual water-conducting cells of xylem tissue. The parenchyma cells function in storage and the fibers function in support. Phloem transports the carbohydrate products (sugars) of photosynthesis throughout the plant.