8. 



XYLEM (zi' lem) (Gr. xylon, wood) 



A. TRACHEIDS (trak'eid) (L. irac/izfl^ windpipe, or tube) 



B. TRACHEAL VESSELS (TUBES) 



C. XYLEM PARENCHYMA 



D. XYLEM (WOOD) RAY CELLS 



E. XYLEM (WOOD) FIBERS 

 PHLOEM (flo'em) (Gr. phloios, smooth bark) 



A. SIEVE TUBES 



B. COMPANION CELLS 



C. PHLOEM PARENCHYMA 



D. PHLOEM RAY CELLS 



E. PHLOEM FIBERS 



Kinds of Plant Tissues (Figs. 18 and 19) 



SHAPE, SIZE, AND ARRANGE- 

 MENT OF CELLS 



LOCATION AND 

 FUNCTIONS 



L MERISTE- 

 MATIC 



Small, thin walled, frequently cube 

 shaped, actively dividing by cell 

 division (mitosis) to form and dif- 

 ferentiate permanent, mature tis- 

 sues; cells closely packed and usu- 

 ally with no intercellular spaces. 



Found near the tips of roots 

 and in buds of stems (ter- 

 minal, or apical meri- 

 stems), between bark and 

 wood of trees (cambium), 

 in bark of trees (cork 

 cambium), or where ex- 

 tensive growth occurs; 

 commonly called 

 "growth" tissues. 



2. EPIDER- 

 MAL 



Usually one cell thick; outer cell wall 

 often thickened with a waxy, water- 

 proofing substance, cutin; cells 

 usually colorless, except crescent- 

 shaped guard cells, which contain 

 green chloroplasts and which con- 

 trol the epidermal pores, or stomata 

 (stom'ata) (Gr. stoma, opening) 

 for exchange of gases; occasionally, 

 red, purple, or bluish pigments in 

 cell sap may give color to leaves, 

 etc. (Figs. 18, 19). 



Found on surface of leaves, 

 flower parts, fruits, young 

 roots, and stems; conserve 

 moisture and give me- 

 chanical protection 

 against injury, entrance 

 of parasites, and poison- 

 ous materials. 



3. 



PAREN- 

 CHYMA 



Usually spherical or ovoid, but some- 

 times cylindroid, with large central 

 vacuole; usually thin cell walls; 

 numerous intercellular spaces; pro- 

 toplasm inay remain alive for long 

 periods of time. 



Very common and abun- 

 dant, occurring in prac- 

 tically all parts of higher 

 plants; colorless paren- 

 chyma of roots and stems 

 store water and foods; 

 green, chloroplast-bearing 

 cells of internal tissues of 

 leaves photosynthesize 

 foods; when parenchyma 

 contains chloroplasts, it is 

 called chlorenchyma 

 (klor -eng' ki ma) (Gr. 

 chloros, green; engchyma 

 infusion) . 



4. COLLEN- 

 CHYMA 



May be somewhat elongated, with 

 pointed, blunt, or oblique ends; 

 cell walls thickened with cellulose 

 at corners or elsewhere; protoplasm 

 may remain alive for long periods. 



Commonly occur beneath 

 the epidermis in younger 

 parts of plants as well as 

 in certain older parts 

 (petiole of leaf) ; give 

 support and strength. 



