GARDENING TERMS EXPLAINED 511 



True hybrids are usually infertile, i.e. do not produce seed. In the 

 animal world the mule is almost the only known hybrid. 



In-arching 1 . This is a processof propagation not commonly adopted 

 except in the case of certain plants that have hard wood, such as Oranges, 

 Camellias, and others. It is occasionally used in connection with Vine 

 preparation. The process necessitates the bringing together of two 

 branches of about equal size, or a young plant in a pot and a branch of 

 an established plant. Just at the place in each case where the stems 

 are to meet, a slice of some 3 inches in length is cut out with the aid of 

 a sharp knife from the sides of each stem. The two cut surfaces are 

 then brought close together and the two stems are neatly tied together 

 and sometimes clayed over or coated with grafting-mat or with moss 

 tied round them, and kept damp. In time, when the two sections have 

 united, the top of the branch on the one plant is cut off, and the stem 

 and root of the other, and thus a new plant on an old one is obtained. 



Layers. The propagation of plants by layers is work that should 

 have great attraction for the novice. It is most practised on Carnations 

 in the flower garden, but many shrubs and trees can be increased in this 

 way. To make a layer it is generally necessary to do more than merely 

 bury a branch partially in the ground. When only this is done, rooting 

 seldom follows. It is necessary to " tongue " the layer with a sharp 

 knife. By " tongued " is meant cutting a slit about an inch long on 

 the under side, and it must pass half-way through the stem towards 

 the leaves or point, but must not sever it from the plant. When the 

 slit is buried in the soil it must be kept open. Sand placed round it 

 helps to form roots later. Sap formed in the leaves becomes in its 

 return rootwards partially diverted into the tongue slit, and roots are 

 soon formed. 



Leaf Mould. It is naturally assumed that this material is the pro- 

 duct of leaves. That is so, but only of tree leaves. The best leaf mould 

 is made with the leaves of hard-wooded trees such as Beech, Oak, Elm, 

 Lime, and Plane, and, if possible, for potting purposes, Horse-chestnut 

 and Sycamore leaves should be avoided. The first-named trees give 

 more woody matter than the latter. Leaves collected to form mould 

 should be free from other matter, and be put into a heap to decay. 

 Put them together whilst damp, or if dry then well saturate them with 

 water. The heap must be occasionally turned and mixed to ensure 

 decomposition, and to enable hard leaves to become thoroughly decom- 

 posed fully a year is necessary. A good dusting of soot when the heaps 

 are being turned helps to kill insect-life. When mould is quite formed 

 it may be stored for use in tubs or boxes. 



Lean-to. Many small greenhouses, vineries, Peach, Cucumber, 

 and other forms, as well as ordinary plant glasshouses, are built as " lean- 

 to's." Thus in good gardens it is usual to see long ranges of such 

 houses built to a tall wall facing south, and behind facing north a long 

 row of lean-to sheds, stores, and other such things. Lean-to houses 

 having but one glass face, and that to the sun, are soon heated, and 

 because they have a thick brick wall at the back which absorbs much 



