lo THE STORY OF PLANT LIFE 



the loss of water, disease or injury, being often pro- 

 vided with a layer of cork. In the cuticle of leaves 

 are the stomata for transpiration and entrance of 

 carbon dioxide gas, and intercellular spaces for 

 respiration, for carbon dioxide gas to enter, and for 

 transpiration, etc. The epidermal cells are usually 

 colourless. They are filled with water, which they 

 serve to store up to retain the plant in a state of 

 turgescence and to protect the chloroplasts. 



The primary cortex consists of collenchyma ex- 

 ternally, parenchyma, stone-cells, and endodermis or 

 the starch-sheath. The collenchyma is to impart 

 strength. The parenchyma sometimes contains 

 chloroplasts which manufacture carbohydrates, and 

 it also stores up some reserves, as well as conducts 

 materials. The stone-cells or short sclerenchyma 

 cells serve for protection and impart strength. The 

 bast fibres also impart strength. The endodermis or 

 starch-sheath contains much starch, and is gravi- 

 perceptional. Intercellular spaces, found in the rest 

 of the primary cortex, are absent in the starch-sheath. 



Between the last and the phloem is the pericycle. 

 This contains bast fibres in many cases, or 

 strengthening tissues. The parenchyma of the 

 pericycle contains chloroplasts, and this also con- 

 ducts and stores up carbohydrates, etc. 



In the primary vascular bundle the phloem comes 

 outside. It is the great conducting agent of the 

 food-materials from one part of the plant to the 

 other, being as well developed in the leaves, etc., as 



