LENTICELS 



193 



raised above the surface of the bark will be noticed. These are 

 lenticels. Cut cross sections of bark and note structure. 1 



Cut a section of a twig bearing lenticels and pass it through a 

 stopper holding a piece of bent glass tubing, as in the previous 



FIG. 94. O, stoma on stem of Sambucus nigra from which a lenticel is formed. 

 I, stoma in the first stage of development toward the formation of a lentical. 2, 

 young lenticel formed by rupture of epidermis near the stoma. ep, epidermis, suberized. 

 tt, cells of cortex and epidermis undergoing division, a, b t cells, derived from an 

 initial cortical cell by repeated division. 3, c t cl t atrophied cells. sub, cells with sub- 

 erized walls, a, b, c, d, concave layer of active cells, d, cl, cortical cells beginning 

 division. After Devaux. 



experiment. Seal in the stopper without abrading the bark, and 

 also seal the upper end of the twig carefully with wax. Now 

 apply suction to the glass tube, and note the exit of air-bubbles 



1 Devaux, M. H. Recherches sur les lenticelles. Ann. Sc. Nat. Bot, 8. 

 12 : I. 1900. 



