RAPHANUS SATIVUS 



307 



quent lateral connections between the main bundles, and the ulti- 

 mate veinlets end blindly in the mesophyll. 



Stomata are more abundant in the lower than the upper epider- 

 mis. They are formed by successive divisions of an initial epi- 

 dermal cell in which anticlinal walls are laid down so that the 



Fig. 154. A, diagrammatic transection of young stem and petiole showing vascular bun- 

 dles ; B, same, of petiole ; C, transection of sector of blade ; D, epidermal hair with basal 

 cells (much enlarged); E, surface view of epidermis showing ontogeny of stoma : i-i, t.-i, 

 and 3-3 indicate successive anticlinal walls which divide initial cell into mother cell and 

 surrounding accessory cells. A final division of mother cell forms two guard cells ; F, tran- 

 section of sector of lamina of cotyledon : ^/>, epidermis; gc, guard cell ; /ir, epidermal hair; 

 / St), intercellular space; I g, leaf gap; pal, palisade cells; spo, spongy cells; sto, stoma; 

 f, vein. 



