Cells and Tissues 



69 



w 



4. As to fusion — 



[a) Without protoplasmic contents and with markings — 

 Vessels, end fusion complete, found in wood, 

 conveying transpiration current and air. 

 With protoplasmic contents without markings — 

 Sieve tubes, ends perforated, found in phloem, 



carrying elaborated food. 

 Latex vessels, end fusion complete, forming a 

 network, found in various parts, carrying latex. 

 All of the cells mentioned here except latex tubes may be 

 found in the oak stem (Fig. 72). 



Fig. 70. — Cell structure. A, young parenchymatous cells ; p, protoplasm ; 

 k, nucleus ; kk, nucleolus ; B, older cells showing vacuoles ; j in C, the vacuoles 

 have become larger ; y, the protoplasm has withdrawn from the wall and the 

 cell will become inactive. 



5. As to contents — 



A typical cell has 



{a) Protoplasm consisting of cytoplasm 



with outer layer, ectoplasm. 



inner layer, endoplasm. 



nuclear membrane, kinoplasm. 



{b) Nucleus, with nucleolus. 



