Wedge- and cleft-grafting are used in many instructive ways with tubers that have lost their crown-buds, and in grafting one species of cactus on another, and in grafting very many greenhouse- and house-plants. It is often curious, if not profitable, to see two varieties of herbaceous plants upon the same roots. It is easy to graft the finest flowering species of cactus on common stocks, as shown in Fig. 54, where the parts arc held together with a pin, but we have found it best to cover the wounded parts with waxed paper. Peonia tubers that have lost the crown-buds can be grafted in the same way ; also the dahlia tubers, the fleshy roots of the hollyhock, ipomcea, and other fleshy roots. It is also quite possible to unite two fruits of the same species when in a growing condition and both connected with the parent tree. One-half of each is cut away and the two halves left are neatly joined and covered with a sack of oiled paper. Under glass it is easy to unite the fruits of tomatoes, cucumbers, and squashes in this way. Such work only has value in the way of illustrating the principles of grafting.
Fig. 54. Cleft - grafting of cactus.