Trees which do not shed layers of dead tissues regularly have increasingly rugged bark as they age. This can often be observed by noting the relatively smooth nature of the top of a trunk in comparison with the older parts at the bottom. With age, the pressure from within causes the surface to crack and the resulting deep fissures are typical of many trees. The way trees develop such features can be diagnostic and one of the most distinctive is the Sweet Chestnut (Caslanea saliva) which usually cracks in spirals. Read the rest of this entry »

To examine the rings of a tree without felling it, cores can be taken by boring into the wood with a hollow cylinder. By counting them inwards each ring can be accurately dated, the age of the tree can be determined and past climatic conditions can be inferred. For accuracy a number of trees is sampled and the ring widths compared. If they coincide, as they normally do, then narrow rings will indicate a poor growing season, probably one with a spring and early summer drought, Read the rest of this entry »

Generally, however, the vascular bundles in a straight piece of grass stem — Maize (Zea mays) being a good example — do not run parallel to the sides but weave from the inner part of the stem to the outer, returning inwards after the leaf traces have branched off. So the vascular tissue forms a series of spirals through the stem. As well as having a different arrangement in the stem, these vascular bundles are different in their individual make-up, there being no layer of cambium between the xylem and the phloem. This means that they cannot develop a woody, strengthening tissue as can dicotyledonous plants. There are exceptions, however, as in the palms and allied woody-stemmed monocotyledons. Read the rest of this entry »