196 PLANT GROWTH 



The stele is the conducting portion of a root including the xylem, phloem, 

 cambium, and pericycle. It is surrounded by the endodermis and 

 cortex. 



Stipules are the two appendages at the base of most leaves. They are of 

 various forms, but frequently are small bract-like structures. 



The stoma is an opening through the epidermis of a leaf between two 

 guard cells through which the gases pass, i.e., carbon dioxide, oxy- 

 gen, and water. 



Symbiosis is the living together of two kinds of organisms in such a way 

 that each is benefited. 



Transpiration is the evaporation in the leaf and loss of moisture from 

 a plant to the atmosphere. 



Vacuole is a space or cavity in the protoplasm of a cell containing other 



matter, i.e., the cell sap. 

 Variation is a change in the characteristics of the offspring from those 

 of the parent. It is usually the result of the environment during 

 growth or of a new combination of the chromatin at the time of the 

 fertilization of the egg cell. 



The xylem is the water conducting portion of a plant made of elongated 

 cells, which generally become woody as they get older. 



