ROOT. 121 



14. Other kinds of vascular tissue are incapable of unrolling, but break 

 when stretched. 



15. Spiral vessels are not found in the wood or bark, and rarely in the 

 roots of plants. 



16. Vascular tissue of other kinds is confined to the root, stem, veins of 

 leaves, petals, and other parts composed of leaves. It is not found in bark. 



17. The common office of the tissue is to convey fluid or air, and to act 

 as the receptacle of secretions. 



18. Cellular tissue conveys fluids in all directions, absorbs with great 

 rapidity, is the first cause of the adhesions that take place between con- 

 tiguous parts, and is the principal receptacle of secreted matter. 



19. Adhesion will take place at all times during the growing season, 

 when the cellular tissues of two dilTerent parts, or of two different plants, 

 is kept for some time in contact ; but as none but tissues of nearly the 

 same nature will adhere, grafting and budding, which are caused by the 

 adhesion of contiguous parts, can only take place either between different 

 varieties of the same species, or between nearly related species ; and even 

 then only when the corresponding parts of the scion or bud, and the stock, 

 are placed in contact. 



20. Woody fibre conveys fluid in the direction of its length, gives stiff- 

 ness and flexibility to the general system, and acts as a protection to spiral 

 and other delicate vessels. 



21. Spiral vessels convey oxygenated air. 



22. Other vessels probably conduct fluid when young, and air when old. 



23. As the bodies of which all tissue is composed are perfectly simple, 

 unbranched, and regular in figure, having, when elongated, their two extremi- 

 ties exactly alike, they are more or less capable of conveying gaseous mat- 

 ter or fluids in any direction ; and, consequently a current may be reversed 

 in them without inconvenience : hence inverted cuttings or stems will grow. 



24. All parts of plants are composed of tissue, whether they be soft, as 

 pulp ; or hard, as the bony lining of a peach. 



25. With regard to Horticultural operations, the parts of plants should 

 be considered under the heads of Root (II.) ; Stem (III.) ; Leaf Buds 

 (IV.) ; Leaves (V.) ; Flowers (VI.) ; Sexes (VII.) ; Fruit (VIII.) ; and 

 Seed (IX). 



II. Root. 



26. The Root is the part that strikes into the earth when a seed begins 

 to germinate, and which afterward continues to lengthen beneath the soil. 



27. It is also the part which is sometimes emitted by the stem, for the 

 purpose of absorbing nutriment from the atmosphere : as in Ivy, Air- 

 Plants, Vines, &c. 



28. It is distinguished from the stem by the absence of leaves in any 

 state, of regular leaf-buds (IV.) ; of evaporating pores or stomata (131) j 

 and of pith in Exogenous plants. 



29. Therefore, such underground bodies as those called Tuber (61) in 

 the Potato 5 Bulb (96) in the Onion; and solid Bulb or Cormus (61) in 

 the Crocus, are not roots. 



30. The office of the root is to absorb food in a fluid or gaseous state ; 

 and also to fix the plant in the soil, or to some firm support. 



11 



