326 THE BIOLOGY OF THE PLANT 



2. The sclerenchyma. — How do you distinguish 



it from the epidermis ? What is the color of 

 its cell -walls? What are its cell contents? 

 Are the walls stratified, pitted, or marked in 

 any way ? Note the line (section of the mid- 

 dle lamella) between the adjacent cell-walls. 

 Are there any intercellular contents? Does the 

 'peripheral sclerenchyma pass entirely around 

 the stem ? Examine the groups of central 

 sclerenchyma. How many are there ? Of what 

 are they composed ? Are the component parts 

 different from those of the peripheral scleren- 

 chyma ? Draw some of the sclerenchyma. 



3. The parench.ym.a.— Is this sharply marked off 



from the sclerenchyma ? How do its cells com- 

 pare in shape, size, color, and contents with 

 those of the sclerenchyma ? Compare them 

 with the parenchyma cells seen in Marchantia. 

 Make drawings of the parenchyma. 



4. The fibro- vascular bundles. — Are they visi- 



ble to the unaided eye? How many do you 

 find ? Are they arranged in definite positions ? 

 What is their shape? Are they sharply sepa- 

 rated from the surrounding tissues i I^ote that 

 each bundle consists of a group of large, thick- 

 walled, empty cells, the xylem portion of the 

 bundle, surrounded by a band, the phloem por- 

 tion, of smaller, thinner-walled cells, with gran- 

 ular contents. Outside of this is a narrow band, 

 the buudle-sheath, of cells, next which comes 

 the parenchj^ma. As sections of the rachis are 

 much more easily cut than of the rhizome, the 

 detailed examination of the fibro-vascular bun- 

 dle will be made when the leaf is studied. Stain 



