364 RELATION TO ENVIRONMENT. 



714. Physiological Classification of Tissues. 

 Formative Tissue. 



Thin-walled cells composing the meristem, capable of division and from 



which other tissues are formed. 

 Protective Tissue. 



Tegumentary System. Epidermis, periderm, bark protecting the plant 

 from external contact. 



Mechanical System. Bast tissue, bast-like tissue, collenchyma, scler- 



enchyma, afford protection against harmful bending, pulling, etc. 

 Nutritive Tissues. 



Absorptive System. Root hairs and cells, rhizoids, aerial root tissue, 

 absorptive leaf glands, absorptive organs in seeds, haustoria of para- 

 sites, etc. 



Assimilatory System. Assimilating cells in leaf and stem. 



Conductive System. Sieve tissue, tracheary tissue, milk tissue, conduct- 

 ing parenchyma, etc. 



Food-storing System. Water reservoir, water tissue, slime tissue, fleshy 

 roots and stems, endosperm and cotyledons, etc. 



Aerating System. Air spaces and tubes, special air tissue, air-seeking 

 roots, stomatesj lenticels, etc. 



Secretory and Excretory System. Water glands, digestive glands, resin 



glands, nectaries, tannin, pitch and oil receptacles, etc. 

 Apparatus and Tissues for Special Duties. 



Holdfasts. 



Tissues of movement, parachute hairs, floating tissue, hygroscopic tis- 

 sue, living tissue. 



For perceiving stimuli. 



For conducting stimuli, etc. 



