Stiff and hard-wooded plants do not often "strike" or root readily, and in order to facilitate rooting the branch is wounded at the point where a new plant is desired. This wounding serves to induce formation of adventitious buds at that point, and to check the growth of the branch at the tip. It is a common practice to cut the branch about half in two obliquely, on the lower side. This operation is known as "tongueing." "Ringing" or girdling, twisting, notching, and various other methods are employed, none of which, perhaps, possess any peculiar advantages in general practice. Some propagators cut all the buds from the covered portion. In this case the free and protruding end of the layer is expected to form the top of the new plant. "Arching," or very abrupt bending, as in serpentine layering, serves the same purpose and is the only attention necessary in most vines. When large numbers of plants are desired, as in commercial nurseries, it is often necessary to cut back the parent plant to the ground, or very nearly so, for the purpose of securing many shoots fit for layering. A plant which is cut back in the spring will produce shoots fit for layering the following spring; or some species will produce them in abundance the same year if layers of green or immature wood are desired. These parent or stock-plants are called "stools" by nurserymen. [Illustration: Fig. 21. Mound Layering of Gooseberry.] In many species layerage is performed to best advantage by heaping earth over the stool and around the shoots. This is known as _mound_ or _stool layering_. The shoots send out roots near the base and straight, stocky plants are obtained. The English gooseberries are almost exclusively propagated in this manner in this country. Fig. 21 shows a row of mound-layered gooseberries. The shoots are allowed to remain in layerage two years, in the case of English gooseberries, if the best plants are wanted, but in many species the operation is completed in a single season. Quinces and Paradise apple stocks are extensively mound-layered. The practice is most useful in those low plants which produce short and rather stiff shoots. As a rule, the best season for making layers is in spring when the leaves are forming. Rooting progresses rapidly at that season. Many plants "bleed" if layered earlier in the season. Hardy shrubs may be layered in the fall, either early or late, and if an incision is made, a callus will have formed by spring. If rapid multiplication is desired, the soft and growing shoots may be layered during the summer. This operation is variously known as "summer," "herbaceous," "green" and "soft" layering. Comparatively feeble plants usually result from this practice, and it is not in common favor. [Illustration: Fig. 22. Pot layerage.]