Definition of guano. : a fertilizer containing the accumulated excrement of seabirds or bats; broadly : excrement especially of seabirds or bats.
This is a cross section through the small intestine. The tall, vertical cells seen at the top of the tissue are columnar cells (one is shown - red arrow), which make up simple columnar epithelium (the cells at the bottom of the image are connective tissue, which will be discussed later). Since columnar cells are quite thick, they do not readily allow passive diffusion.
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.