1133. To propagate and preserve from degeneracy approved varieties of vegetables, it is in general necessary to have recourse to the different modes of propagating by extension. Thus, choice apples and tree fruits are preserved and multiplied by grafting; others, as the pine-apple, by cuttings or suckers; choice carnations by layers, potatoes by cuttings of the tubers, &c. But approved varieties of annuals are in general multiplied and preserved by selecting seed from the finest specimens, and paying particular attention to supply suitable culture. This part of culture is the farthest removed from nature; yet there are, notwithstanding, examples of the fortuitous graft ; of accidental layers; of leaves (as of the Cardamine pratensis), or detached portions, forming natural cuttings, dropping and taking root.
