How Cells Are Arranged in Ani?nals and Plants 1 3 3 



of an animal so are the tissues. Plants 

 have no muscle, connective, nerve, or 

 blood tissues. But they do have tissue 

 which resembles the epithelial tissue of 

 animals. It forms a membrane covering 

 leaves, young roots, and stems and also 

 forms small amounts of gland tissue. If 

 you did Exercise 6 in Problem i of this 

 unit you have seen it. The other tissues 

 of a plant bear little resemblance to ani- 

 mal tissues. Many parts of a plant have 

 groups of thin-walled cells containing 

 large vacuoles. This tissue is called par- 

 enchyina (per-en'kim-ma). Parenchyma 

 cells may or may not have chloroplasts. 

 Most roots and stems have large amounts 

 of woody fibers with strong cell walls 

 and they have ducts of various kinds, as 

 well as other tissues. Some of these are 

 shown in Fig. 180, page 155. The tissues 

 consisting of woody fibers and ducts are 

 found, too, in the veins of leaves. 



Living things are fundamentally alike. 

 Living things consist of protoplasm. Most 

 of them consist of many cells. In many- 

 celled organisms the groups of similar 

 cells form tissues, and groups of tissues 

 are organized into organs; the organs 

 make up the organism. This is true of 

 both animals and plants. 



Fig. 160 Cells ni opion skin.- This tissue some- 

 ivhat resembles the epithelial tissue of animals. 

 Which parts of the cell do you recognize? 



(RICHARD ST. CLAIR) 



get a good idea of several of these tissues 

 by studying the tissues in a frog as de- 

 scribed in Exercise 2. 



Tissues in higher plants. As in animals, 

 plant cells are arranged in groups or tis- 

 sues; and various tissues together make 

 up the organs, such as the root, the stem, 

 and the leaf. Just as the organs of a 

 plant are quite different from the organs 



Questions 



1. In what ways do cells of an organism differ from each other? Why 

 is it possible for you to learn much about your own cells by studying 

 other animals? 



2. Define a tissue. Describe a tissue which has intercellular matter. Was 

 your definition of tissue complete? List the tissues found in a human 

 arm, beginning with the outside. 



3. Define the term "organ." Explain the difference between an organ 

 and an organism. How is the word "function" used in reference to 

 cells, tissues, and organs? 



4. Name an organ system in the human body. 



