If, however, instead of allowing the basal part of the amputated branch to protrude as a stump, we cut it off close to the stem, and shave the section flush with the normal surface of the latter, the callus formed by the cambium, etc., rapidly grows over the surface, and soon forms a layer of cambium continuous with that of the rest of the stem. The wound heals, in fact, much as if it were a strip-wound, and beyond a slight prominence for a year or two no signs are visible from the outside after the occlusion. Of course these matters depend on the relative thickness of branch and stem, and if much wood is exposed the dangers of rot and a resulting hollow in the stem are increased. It is interesting to note how much thicker the callus lips are at the sides of the wound than above and below, owing to differences in the distribution of the nutrient materials. _Stool-stumps._--When a tree is felled, the stump may, if the section is close to the ground and kept moist, begin to form a thick rim-like callus round the wood, in which adventitious buds soon make their appearance, and grow out into so-called _Stool-shoots_. The products of assimilation of these, and the stores accumulated in the stump, often suffice to feed the callus sufficiently to enable it to grow over and completely occlude the wound, if the wood surface is not too large, or so long exposed that rotting processes have meanwhile set in. _Ringing._--If the strip of cortical tissues and cambium is removed all round the stem, exposing the wood in a form of a ring, complications may ensue owing to the following circumstances. A well-marked callus appears at the upper edge of the wound, because, the transpiration current up the young wood not being stopped, plenty of water and salts from the soil can reach the leaves; but the nutritive materials supplied by the latter are accumulated at the upper lip of the wound owing to the stoppage there of their descent in the phloem, cortex, etc. No such callus-lip appears at the lower margin of the wound owing to want of these supplies. Consequently the occlusion and healing of the ring-wound only takes place from above downwards, and if the ring of cortical tissues removed is a broad one, the healing may be a long process, or may even be indefinitely delayed, a thicker and thicker callus projecting over from above. For similar reasons no annual wood layers are formed below, but only above the wound, and thus the branch or tree may die. The latter contingency is the more likely the further up the tree the ringing takes place, owing to the risk of drying up which threatens the exposed wood, and to the consequent interruption of the transpiration current, and the likelihood that lateral shoots below the wound may divert the water to their own leaves. If the ringing occurs low down on a stem, and the environment remains damp, the upper thick callus may put out new roots; the part above the wound then behaves like a cutting.