CELL-CONTENTS AND FORMS OF CELLS. 229 



and Tunmann would seem to show that the secretion in the 

 glandular hair arises in a subcutaneous layer of the wall, which has 

 been termed a " resinogenous layer." Even De Bary, with char- 

 acteristic caution, has stated that the secretion found in the walls 

 of glandular hairs originates in the wall even though the ma- 

 terials for its formation must arise in the protoplasm of the cells. 

 In the study of glandular hairs the method of Tunmann may 

 be followed (Bcr. d. d. phartn. Gescllsch., 1908', p. 513). Fresh, 

 or even dried, material may be used. Surface sections are made 



FIG. 124. A glandular hair from the young leaves of Lavandula vera seen in different 

 stages in the course of three days, showing that the underlying cells remain of the same 

 size and structure, but that there is a gradual increase in the glandular area or resinogenous 

 layer. After Tunmann. 



and examined in aqueous solutions containing 10, 20, 30, or 40 

 per cent, of hydrated chloral. The 10 per cent, solution is used 

 first, then the 20 per cent., etc. The proper solution renders the 

 hair transparent, dissolves the resin, and, if the cover-glass is 

 moved sidewise, the cuticle bursts, showing the resinogenous 

 layer. Tunmann distinguishes three different types of glandu- 

 lar hairs, depending upon the character of this resinog- 

 enous layer. ( i ) In which by this treatment there separate 

 small rod-like crystals resembling bacteria, as in Fig. 125, A, B, C. 

 (2) A second type is given in which vacuoles occur consisting of 



