9 8 BOTANY FOR BEGINNERS CHAP. 



(ii) To some of the root-hairs particles of soil adhere. 

 This adhesion of the root-hairs to particles of soil is due to the con- 

 version of the outer layer of the cell-walls into mucilage. 



EXPT. 92. Pull off a small piece of the epidermis of a leaf of the 

 Sunflower ; mount in water, and examine under a low power. Note 



The multicellular hairs which are scattered over the surface of the 

 leaf. 



VASCULAR TISSUE. 



Vascular tissue. If a skeleton leaf be examined it will be 

 found to consist of a number of hard fibres ; these are the vas- 

 cular bundles. These bundles form the conductive tissue of 

 the plant, that is, they conduct water from the roots up the 

 stem, to the leaves, and the elaborated sap from the leaves to 

 those parts of the plant which need it. Such bundles are also 

 the principal supporting tissue of the plant and form the frame- 

 work upon which the softer parts are fixed. The bundles always 

 resist decay longer than the other parts of the plant, and in a 

 skeleton leaf or stem are the only parts present. In the higher 

 plants there are two principal types of vascular bundles, they are 

 known as open and closed bundles. Open bundles are found in 

 Dicotyledonous plants and closed bundles in Monocotyledonous 

 plants. 



Structure of Bundles. If a vascular bundle of the 

 Dicotyledonous type be examined under the microscope, there 

 will be seen : 



(1) The Xylem, which is nearest the centre of the plant. 



(2) The Phloem, which is always the portion of the bundle 

 most removed from the centre of the plant. 



(3) The Cambium, which lies between the xylem and 

 phloem. 



Xylem. The xylem is the woody portion of the bundle, and 

 in the vascular bundle of the stem it is always found nearest to 

 the pith. It consists of a number of vessels and parenchyma 

 cells. The vessels which are- found in the xylem are spiral 

 (p. 93), annular (p. 93), reticulated (p. 93), and pitted (p. 93). 

 The spiral vessels are the nearest to the pith, then come the annular 

 vessels, and these two kinds together make up the first-formed 

 xylem, called protoxylem. The reticulate vessels come 

 next, and the pitted vessels are to be found close up to the 

 Cambium. Scattered about among the vessels, fibrous cells are 

 to be found. These fibrous cells are long and narrow, and in 



