6 DESCRIPTION OF 



First Class has a more complicated, consequently, 

 a more firm, and durable structure than the second. 



We will now examine the Stems, where the more 

 important difference of structure, (the woody fibre) is 

 best seen. 



Cut off a branch, of any tree of our woods or 

 gardens, and you can see the structure of a Dicotyle- 

 donous Stem : we can find no trees of the second Class 

 in this country, except in hot-houses. But a piece 

 of Cane or Bamboo, (of which chairs, and walking- 

 sticks are often made,) will, even in their dry state, 

 show you the formation of a Monocotyledonous Stem 

 very weU. PL I. A 2. B. 2. 



In the First Class, the PITH is in the centre, 

 WOOD around it, and BARK outside. A new layer 

 of Wood is formed on the outside of the old each year : 

 the newest Wood is white, and called Alburnum. The 

 Bark is increased by a succession of layers within the 

 old, the newest Bark being always next to the Albur- 

 num. The MEDULLABY BAYS, connect the Pith with 

 the Bark, and are called the Silver Grain, in wood. 



In the Second Class, the Stem is not increased by a 

 succession of layers on the outside of the old ones ; but 

 consists of Cellular Tissue, in which the woody fibre 

 (Vascular Tissue) is inserted in confused bundles, or 



