44G 



Lloyd : Anatomy of Chrysoma pauciflosculosa 



pellucid areas is surrounded by a sulcus. In drying they shrink 

 inwardly, giving rise to the term "pitted" as applied to the leaf 

 surface, which however would better be described as a mosaic. 

 Both sides of the leaf have the same appearance, the reason for 

 which will be better understood by an examination of the internal 



structure. 



The sulci just referred to are caused by the dipping down of 

 the epidermis on both sides of the leaf to a depth equal approxi- 



FlG. I. Transverse section of leaf, through the midrib and two pairs of air 



chambers. 



mately to one third of the thickness of the leaf. (Fig. I.) The 

 epidermal cells which line the sulcus are of gradually decreasing 

 depth, the deeper they are placed. Between the sulci the epi- 

 dermis stretehes almost without support. 



The arrangem 



ent of 



the mesophyll is such that there is thus formed a disposition of 



Fig. 2. 



Transverse section through a stoma. 



tissues which suggests at once the well-known air chambers of the 

 liverwort, Marchantia. In the roof of epidermal cells, which are 

 cuticularized both within and without, are found the stomata, 

 one of which is shown in detail in Fig. 2, in which are delineated 

 the hinge line (Jt) and an inner guard ridge (r) making a sensitive 

 and effective stoma. The effectiveness is heightened by the ac- 



