196 THE ELEMENTS OP VEGETABLE HISTOLOGY 



tissue which may show stomata and trichomes. The 

 parenchymatic tissues of stigma, style and ovary 

 consist of loosely connected cells showing large inter- 

 cellular spaces. These parenchyma cells usually contain 

 chloroplasts. The fibro-vascular tissues are of great 

 importance in the style and ovary, as in the former 

 organ they provide a channel for the descent of the 

 pollen tube, and in the latter they conduct nutrients 

 to the developing embryo. The ovules are covered 

 with a thin but resistant epidermis, within which are 

 parenchyma cells containing large amounts of nutrient 

 material and the developing embryo. 



Stem Tissues. — The stem tissues of the flower 

 are in every respect similar to other plant stems and 

 exhibit the elements noted in the section on Primary 

 Stems (Chapter XIV). Stone cells are of frequent 

 occurrence in flower stems, and their presence often 

 affords a means of detecting excess stems in flower 

 powders. 



CELL CONTENTS 



The cell contents of flowers are stored within the 

 parenchyma cells of the different floral organs. The 

 protoplasmic cell contents include chlorophyll and 

 various other pigments. The non-protoplasmic con- 

 tents include calcium oxalate crystals and the vola- 

 tile oils secreted by glandular hairs. Starch is rarely 

 present. 



FUNCTIONS OF FLOWER TISSUES 



The functions of the different structures present 

 in flowers may be summarized as follows : 



