24 BOTANY 



physiology, the main work of the anatomist deals with 

 the tissues themselves, and concerns itself with their 

 individual characters and the comparative study of 

 their development in the different orders of organisms. 



The plant body is composed of jive principal kinds 

 of tissue. These are the Epidermis, or skin, with its 

 hairs and other minor developments ; the Parenchyma, 

 forming the general ground tissue of the plant, with a 

 number of minor modifications ; the Sclerenchyma, or 

 thick-walled strengthening tissue ; and the vascular 

 tissue, which is of two kinds, viz., the Wood, which is 

 thick-walled, and conducts water and also helps to 

 strengthen the plant, and the Bast or Phloem, which 

 forms the channel for the passage of the elaborated 

 food-stuffs. For the higher plants, although there is 

 much specific variety, there is a characteristic plan for 

 the arrangement of these tissues in each of the organs 

 root, stem, and leaf. 



In roots there is no true epidermis, but the outer cells 

 of the young root are extended to form long hairs with 

 thin absorbent walls. The parenchymatous ground 

 tissue forms the main mass of the root, and the vascular 

 tissue is a compact, central strand. In most roots 

 there is no pith, and the wood forms a solid mass in 

 the centre with groups of the phloem outside it. This 

 cylinder is shut off from the surrounding ground tissue 

 by a specialised sheath, which is generally much better 

 developed in roots and in the lower plants, such aa 

 ferns and lycopods, than it is in the other organs of the 

 higher plants, though it is sometimes clearly marked 

 in their stems. 



Stems have an epidermis while they are young, and 

 this protective layer is replaced by an ever increasing 

 secondary coat of cork as they increase in size. The 



