18 WALL'S MANUAL 



to end. Vasiform tissue consists of tubes much larger 

 than those of the woody fibre. These tubes may 

 be seen in the cross- section of oak wood. It is 

 chiefly through these that the sap passes in ascending 

 from the roots to the leaves. Laticiferous tissue con- 

 sists of very small tubes and cells, found most abun- 

 dantly in bark and leaves. After the sap has been 

 prepared in the leaf for nourishing the plant, it is 

 called latex. Those vessels of the leaf in which this 

 preparation or elaboration goes on, and those which 

 afterward convey the latex back to the part of the 

 plant to be nourished^ by it, arc formed of the lati- 

 eiferous (latex) tissue. 



These various kinds of tissues hold and transmit 

 the fluids of the plant, the different tubes and cells 

 having no communication with each other except 

 through minute pores. These vessels are sometimes 

 charged with liquid matter, and sometimes with gases. 



BarL The bark is the external covering of the 

 plant, and may be regarded as enveloping every other 

 part of it, except the extremities of the roots and the 

 stigma of the flowers. The outer bark is composed 

 chiefly of cellular tissues. The inner bark consists of 

 cellular and woody tissues. There are little openings 

 in the outer bark called stonata (mouths). These are 

 very minute, requiring the aid of the microscope to 

 see them. They are most numerous on the surface 

 of leaves on parts of the plant of recent growth. 

 These mouths perform important offices, in taking up 

 moisture and gases from the air. 



Glands are minute masses of cellular tissues, of 

 various forms, and situated in various parts of the 

 plant. Their office is to elaborate and discharge the 



