54 



COMPENDIUM OF GENERAL BOTANY. 



dition is fouud useful in all of the three forms of epidermal 

 function. If the contiguous radial walls of the epidermis take a 

 wavy course (whereby their area is also increased), it very materially 

 increases the mechanical resistance to the separation of the contact- 

 walls. In an actual test rupturing of the tangential outer wall 

 took place much more readily than separation of the radial contact- 

 walls. 



The accompanying figures show two small portions of represent- 

 ative epidermal tissue in surface view. 



Fig. 32. 



Fig. 33, 



In Fig. 34 are shown all three epidermal peculiarities quite 

 well developed. Let us consider it more in particular. The genus 



^^od comprises plants adapted to with- 

 stand dry periods ; therefore they have 

 those anatoTnical features which tend 

 to reduce the loss of moisture well 

 developed. The cuticle inclusive of 

 the Guticiblar laj'ers {cs = cuticular 

 layers, c = cuticle, h = cellulose) is 

 ver}^ thick. The cuticula is a thin 

 membrane highly impermeable to 



Fig. 34.— Epidermal cells of the ^a^-e^ It resulted from fatty and 

 leaf of Aloe acinacifolia. , ^^ -\ ' 



(After Haberiandt.) waxy dcposits in the cellulose-mem- 



brane (cuticularization). In many of our indigenous plants this 

 cuticula is exceedingly thin, but is present in all plants; in sub- 

 merged water-plants it is almost reduced to zero (No. 2). 



The thiekne>s of the entire outer wall inclusive of the thickened 



