London Horticultural Society and Garden. 38 i 



degrees of heat, light, and air, to. which they are exposed. To know how 

 to effect these ends, the horticulturist ought to understand something of 

 the nature of plants generally, to be aware of their natural affinities, and 

 to know the climates in which they are indigenous. At the same time, it 

 is perfectly true that an excellent theorist may be unsuccessful in garden- 

 ing, from a want of that dexterity which can only be acquired by practice ; 

 and also that a man may be a good practical horticulturist without know- 

 ing any thing of botany, as he may have learned all that is necessary for 

 the well-doing of the plants under his care empirically, from habit and 

 experience. Knowledge founded only on experience must, however, neces- 

 sarily be extremely limited ; and it is always safer to recur to principles, 

 which must, if sound, be applicable to every possible emergency. 



As a popular instance of the utility of a knowledge of the natural affini- 

 ties of plants, to the practical horticulturist, the professor mentioned the 

 impossibility of grafting a lilac on an apple or a currant tree, notwith- 

 standing the apparent resemblance in shape between its flowers and those 

 of some varieties of the latter genus ; while the lilac might be grafted upon 

 the ash : both belonging to the same natural order, and, of course, an affi- 

 nity existing between them. No union can ever be effected by grafting one 

 plant upon another, unless such affinity exists between them; and the 

 vulgar notion, that it is possible to produce a black rose by grafting a rose 

 on a black currant, Mr. Lindley assured his auditors he considered almost 

 too ridiculous to be mentioned. He added that hybridising was subject 

 to the same laws and limitations as grafting. With regard to the import- 

 ance of a knowledge of the natural climates and habits of plants, the pro- 

 fessor mentioned the fact, that some plants were fertile only on a north 

 wall, while others required the south ; that some would not live in iron 

 hot-houses, while others grew more vigorously in such a situation than in 

 others ; and that these results might have been confidently anticipated, 

 before the experiment was tried, by any one acquainted with the habits of 

 the plants referred to. 



Having thus demonstrated the importance of at least a slight know- 

 ledge of the principles of botany to the practical horticulturist, Mr. Lindley 

 proceeded to take a general view of those principles; and began by 

 considering the nature of plants. All vegetable substances consist of an 

 immense number of atoms, or small parts, held together by the principle 

 of adhesion, and called by the general name of tissue. This tissue is of 

 three kinds : cellular, fibrous, and vascular. Cellular tissue is composed of 

 a great number of small cells or bladders, each formed of a thin imperforate 

 membrane, through which, however, the sap contrives to circulate by 

 means of invisible pores. These cells are of various shapes, and are 

 characterised by their facility in breaking, or brittleness. Numerous 

 vegetable substances are composed entirely of cellular tissue, but others 

 only partially : as an instance of the first, the professor mentioned the 

 fungus which, by Captain Ross and his companions, has been termed red 

 snow. Cellular tissue forms the pith, or medullary substance, of trees, the 

 flesh of fruits, &c. &c. To exemplify the brittleness of cellular tissue, Mr. 

 Lindley exhibited a specimen of Chinese rice paper, made from the 

 medullary substance of the jEschynomene paludosa Roxb. [See Gard. Mag. t 

 vol. v. p. 309.] Fibrous tissue is composed of a number of hollow tubes, 

 tapering at both ends, each not more than the twelve-hundredth part of 

 an inch in diameter, and yet having the vacancy in the centre much larger 

 than the sides. The albumen and inner bark of trees are formed of this 

 substance; the toughness of which the professor illustrated by exhibiting a 

 piece of Russian bast mat, made of the inner bark of the lime. Vascular 

 tissue comprehends the spiral vessels and cylindrical ducts, for conveying 

 air and sap. 



Plants are provided with roots, stems, leaf-buds, leaves, flowers, fruit, 

 and seed; all performing important, though distinct, functions, and all 



