Water-Content of Plants 



49 



supply does not inhibit root-hair production in the ordinary 

 crop plant ; but with strong light it is more difficult to 

 maintain a high moisture content under laboratory con- 

 ditions. 



32. The root-cap. A longitudinal section of the tip 

 p c e 



FIG. 13. Root-tip of corn, high-power study of formative region : 

 epidermis (c), cortex or periblem (c), plerome (p), and root-cap (r). 

 [After Curtis.] 



of the root (Fig. 12) shows a rather complex but interest- 

 ing structure. Protecting the growing tip, there is inva- 

 riably found the well-known structure called the root-cap. 

 The root-cap consists of a mass of cells to which falls the 

 duty or office of a bumper organ. It is very effectively 

 developed by divisions in the epidermal (protodermal) 

 cells of the growing tip parallel to the surface. This mass 



