894 



LAWSONIA 



LAYERING 



glabrous sbnib, with branches spiny or not. Important 

 generic characters are: calyx 4-parted: petals 4: stamens 

 8: capsule globose, 4-celled, rupturing irregularly. 



Alba, Lam. Henna Plant. Lvs. opposite, oval-lanceo- 

 late, entire, short-stalked : fls. paiiicled. Native to In- 

 dia, the Orient, N. Afr. Naturalized in West Indies. 



LAYERING. Figs. 1248-1253. Layering is tlio jiro- 

 cess by which apart of a plant stem is mad.' to pindu.-e 

 roots while still attached to and nourished I'V tli- |>;n>rit 

 plant, so that it may be able to maintain an iii.l*priMl.iit 

 growth. The tendency, under favorable conditions, to 

 produce roots from the cambium zone of some part of 

 the stem is manifested by many plants, especially in the 

 tropics. It may be noticed in the species of Ficus culti- 

 vated in the greenhouse, in Epigaea and Bhus Toxicoden- 

 dron in the woods, in tomato vines in the garden, in 

 grape canes lying on the ground, and frequently in young 

 apple trees when the trunk becomes covered with earth 

 to an unusual depth. With most such plants, rooting by 

 detached parts is easily accomplished, and this being 

 more convenient, layering is generally practiced only with 

 those plants which do not root readily from cuttings. 



The mode of root-production is essentially the same 

 in either case. The right conditions as to moisture, 

 temperature, food supply, etc., seem to stimulate the 

 formation of one or more growing points in the cambium 

 zone. The multiplying cells force their way through the 

 bark, and if favorable soil contact is secured, supporting 

 roots are soon developed. The same results may coiuf, 

 sometimes more readily, from ornear a callus fumu'd in 

 the effort to heal a cut surface. It is when tlu' fuud sup- 

 ply is deficient or the cell action is so slow that the de- 

 tached part would perish before supporting roots could 

 be established, that rooting while the parts are still at- 

 tached to and nourished by the parent plant need be 

 employed. 



The different methods of Layering are simply matters 

 of detail adapted to the varying natures of the plants to 

 be dealt with. Usually branches are selected of rather 

 young wood, which can easily be brought under the soil 

 and which, when rooted, can be removed without damage 

 to the old plant. The most favorable season is generally 

 the spring or time of most rapid cell growth. 



tched at the bottom. 



The methods of Layering may be represented in the 

 following diagram: 



METHODS OF LAYERING 



Bark ruptured. 

 Biirk ringed. 

 Tongiie cut. 

 Tip Liyered. 



Mound- or stool-layer. 

 . Potted or aerial layer. 

 ( Simple layer. 

 < Trench layer. 

 i Serpentine layer. 



As shown in Fig. 1248, a suitablp branch is bent to the 

 ground and held in place by a forked pin, so that rf por- 



Canes 



tion of it is covered with 2 or 3 inches of rich earth, the 

 end being bent to an upright position and fastened to a 

 stake. The bend and consequent rupture of the bark 

 may be all that is needed to obstruct the movement of 

 food-material and cause the development of roots at this 





1249. A layer ringed or girdled at the bottom. 



point. If not, a tongue may be cut not deeper than one- 

 third of the thickness of the branch from below upwards 

 and near a bud or node. In Fig. 1249 a layered branch 

 is shown with a ring of bark removed, a good practice 

 with thick, hard-barked species. 



For many low-branched shrubs, mound- or stool-layers 

 are prepared (Fig. 1250), as follows: In the spring, head 

 the bush back to a series of stubs, which will produce a 

 large number of vigorous young shoots. By midsummer, 

 in some cases, or the following spring, a mound of earth 

 is thrown around the old stool and the base of the new 

 shoots, and from these latter abundant rooting is se- 

 cured, so that by the following autumn or spring they 

 may be separated and set in nursery rows. 



When a branch cannot be brought to the ground, 

 sometimes the earth is brought to the branch by clasp- 

 ing the halves of a broken or specially made pot around 

 a tongued or girdled branch and filling in earth and 

 sphagnum moss to retain the moisture ; or the moss may 

 be held in place by a cone of strong paper (Fig. 1251). 

 It may be necessary to support the pot with a light stand 

 of stakes. Where a moist atmosphere is retained, as in 

 a conservatory, merely a ball of sphagnum bound around 

 the branch with twine will serve an equally good purpose 

 with less trouble. Tbis kind of propagation is known as 

 air-layering, Chinese layering or circuraposition. 



In the case of vines, a cane may be laid horizontally in 

 a shallow trench, cov- 



7 





*^?Visy^.^ 



'Tp?s> 



1250. Mound- or Stoul Layen 



ering a few inches 



induce rooting, and 



leaving a node or two 



exposed for growth , and 



so on to the end. as 



shown by Fig. 12.'>2. 



After young shoots are 



well started from the 



uncovered buds, the 



earth may be filled in to the level of the dotted line. 



In Fig. 1253 is shown what is often called the serpen- 

 tine layer, in which the cane is bent, portions being 

 covered and the intervals left above the ground. It is 

 said that by this means the tendency of the sap to flow 

 to the extremity and there make the strongest growth, 

 is overcome, and even rooting secured the whole length 

 of the cane. This method is often used with quick-grow- 

 ing vines like clematis and wistaria, from which it is 

 possible to secure a succession of layers from the an- 

 nual growth during spring and early summer. 



All of the foregoing operations will be found more 

 readily successful in the More moist situations ; more 

 successful in the nearly saturated atmosphere of the 

 southern states, for instance, than in the comparatively 

 dry conditions of the prairie states. g. c. Mason. 



