262 HISTOLOGY OF STEM OF THE WAX PLANT 



Epidermis 

 PI. I 

 If the stem of a young plant is examined, it will be found covered 

 with a growth of velvety hairs, and numerous adventitious buds will 

 be seen between the internodes. Portions of the epidermis may be 

 easily obtained by drying a piece of stem that has been in alcohol, 

 or they may readily be pulled off from an older part of the plant. It 

 is composed of cells varying from 15 /tt to 100 /^ in length, and from 

 10 to 30 iJi in width, with their greatest diameter parallel to the axis 

 of the stem. The depth of the epidermal cells is more constant than 

 their width or length, being about 20 to 30 /ct. Their outer wall is 

 about 5 At in thickness. Treatment with concentrated sulphuric acid 

 dissolves the rest of the cell and leaves the cuticle as shown on pi. I, 

 fig. 5. Caustic potash causes the outer wall to swell slightly, when the 

 striated cuticularized portion can be seen covered by the more re- 

 fractive cuticle proper. Schultze's solution stains the epidermis orange- 

 rufous, the stain showing over the same portion of the cell walL that is 

 left after the action of sulphuric acid. Hence we may conclude that 

 the external and part of the lateral walls of the epidermal cells are 

 cutinized. 



Trichomes 



PI. I, Fig. 2 



The Trichomes are simple hairs formed by the prolongation of one 

 epidermal cell, and when young are filled with protoplasm. Concen- 

 trated sulphuric acid does not dissolve them, and Schultze's solution 

 stains them the same color as the outer wall of the epidermal cells. 

 Hence I conclude that their cell walls are cuticularized. Their aver- 

 age length is about .4 mm. They are divided by septae into three or 

 more cells. At the base of the hair the wall is equal in thickness to 

 the outer one of the epidermal cells, but soon becomes much thinner, 

 and the greater portion of the hair is bounded by a wall about 2^ /ct in 

 thickness. 



Stomata 

 PI. n. Fig. 3a 



These are most numerous on the youngest portions of the stem, 

 and, with one exception, all I have seen have their opening parallel 



