TtGOT. 



149 



gives stiffness 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 perfect- 

 ly simple, unbranched, and regular in figure, having, when 

 elongated, their two extremities exactly alike, they are more 

 or less capable of conveying gaseous matter 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 parfs of 

 plants should be considered under the heads of Root (II.) ; 

 Sfem (lllj i Leaf buds (I V.) ; Leaves (V.) ; Flowers (VI.) ; Sexes 

 (VII.; Fruit (VIII.); and £e:d (IX). 



II. Root. 



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

 seed begins to germinate, and which afterwards 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 atmos- 

 phere ; 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.) and of pith in Exogenous plants. 



29. Therefore, such underground bodies as those called 

 Tuber (61.) in the Potato ; Bulb (96.) in the Onion; and solid 

 Bulb or Cormus (61.) in the Crocus, are not roots. 



30. The ottice 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. 



31. The latter office is essential to the certain and regular 

 performance of the former. 



32. It is mt by the whole of their surface that roots absorb 

 food; but only by their young and newly formed extremities, 

 called Spoagio/ts. 



33. Hence the preservation of the spongioles in an uninjured 

 state is essential to the removal of a plant from one place to 

 another. 



34. A Spongiole consists of very young vascular tissue (12-) 

 surrounded by very young cellular substance. (5.) 



35. It is therefore one of the most delicate parts of plants, 

 and the most easily injured. 



36. Hence whatever is known to produce any specific dele- 

 terious action upon leaves or stems, such as certain gases (298.) 



13* 



