58 PEACTICAL BOTANY. 



this is hardly necessary, since the components of the several 

 tissues of this stem appear almost uniform in their tangential and 

 radial aspects. 



Starting as before from the periphery, note suc- 

 cessively the following tissues 1 : 



1. The Epidermis, consisting of oblong cells, whose 

 walls and contents present the appearance already 

 observed in the transverse sections. Note the dis- 

 turbance of their normal arrangement around the 

 bases of the larger hairs. 



Beneath the epidermis lies 



2. Collenchyma, consisting of oblong cells with thick 

 longitudinal cellulose walls (blue, Schulze's solution), 

 and thin transverse ends : the contents are protoplasm, 

 with a nucleus and chlorophyll- grains. Below each 

 of the larger hairs the collenchyma gives place to 

 short, thin-walled parenchyma, which, together with 

 the epidermis covering it, forms those emergences 

 on the summit of which the hair is seated. Within 

 this is 



3. Thin-walled Cortical parenchyma, the cells 

 of which are shorter, but wider, than those of the 

 collenchyma ; there is however no sharp limit between 

 them : observe transitional forms. Cell-contents re- 

 semble those of (2), but there is less chlorophyll. 



Note the resin-passages, the course of which is 

 directly longitudinal; they therefore appear as longi- 



1 It is but rarely possible to see all the tissues here enumerated satis- 

 factorily represented in a single radial section, therefore the study of 

 the tissues and their relative positions should be conducted by com- 

 parison of a number of sections one with another. 



