474 



APPENDIX. 



lose projecting into their cavities. The presence of these is 

 probably connected with the feeble development of air spaces 



BORDERED PIT 



^- TRACHEIDAL 



CELLS 



. STARCH CELLS 

 OF MED. RA V 



Pig. 18. Secondary Wood of Pine. 

 Portion of a tangential longitudinal section 



STOMA 



, EPIDERMIS 



_-- HYPODERMIS 



THIN-WALLED 

 . MESOPHYLL 



, ENDODERMIS 

 - PERICYCLE 



- XYLEN/T , 

 - PHLOEM 

 FIBRES OF 

 PERICYCLE 



Fig. 14. Transverse section of Leaf of Pine. 



in the leaf, for they increase the internal surface of the cell- 

 wall, and hence also the excreting and absorbing surface of 



