THE ANGIOSPERMAE : LEAVES 



I02I 



the ratio (R) between internal and external surface was lowest in shade leaves, 

 with reduced numbers of mesophyll cells, (R = 6-8-9-9) and highest in sun 

 leaves of xerophytic type (R = 17-2 - 39-3) the average ratios in mesophytic 

 leaves being between 1 1 -6 and 19-2. Contrary to expectation he found that 





Inflated hair cells 



Upper palisade 



, "» 'i\ ( 1 / Lower palisade 



Fig. 1008. — Ohione portulacoides. Transverse section of 

 leaf showing equifacial structure and protective 

 covering of vesicular hairs on both surfaces. 







Storr\a 



Sdereid 



<^^i«%i^^ 



Endodermis 



Sdererjchyma 



Vascular 

 bundle 



Palisade 



Fig. looq.—Hakea pectinata. Transverse section of leaf 

 showing centric structure. 



