76 PRACTICAL BOTANY 



* * Young Stem. 



IV. Cut transverse sections of a young branch of 

 the Sunflower about one-eighth of an inch in diameter. 



Similar sections may be cut from the hypocotyledonary stem, in 

 which case they will be found to correspond in all important 

 points to the following description, but they will differ in some 

 of the details ; thus hairs will be absent, the bundle-sheath will 

 be more obvious, &c. : it will therefore be best to cut the sections, 

 as directed, from a young branch. 



Mount in glycerine, and passing from the periphery 

 inwards observe successively under a low power 



1. The epidermis, as before a single layer, with 

 hairs of various complexity and shape. Beneath 

 this 



2. Cortical tissue, which is more or less clearly 

 differentiated into 



a. Collenchyma. 



/9. Cortical parenchyma. 



7. Resin-passages. 



8. Bundle-sheath. 



These severally hold the same position, and have the 

 same characters, as were above observed in the older 

 stem, but the tissues are less bulky, and less clearly 

 differentiated from one another. 



The bun die -sheath in the young stem is more easily recog- 

 nized than in the older stem though it will subsequently be 

 still better seen in roots. It is a continuous layer of cells, 

 which have a characteristic dark dot on each radial wall : this 

 is due to reflection of light from the peculiar sinuous waves of the 



