CHAPTER VII 



FLOWERS 



The histological structure of flowers is readily seen in the 

 powder; therefore, in studying flowers, it is not necessary to 

 section the various parts. Each part of the flower should' be 

 isolated and powdered separately and each separated part 

 studied. In each case the powders will contain surface, cross-, 

 and radial sections of the parts powdered. While studying 

 flowers, special attention should be given to the pollen grains, 

 to the papillae of the petals, to the papilla2 of the stigma, and, 

 in certain flowers, to the style tissue. In the composite flowers 

 special attention should also be given to the involucre scales, 

 to the scales of receptacle, and, when present, to the pappus. 

 In addition, attention must be given to secretion cavities, as 

 in cloves. 



POLLEN GRAINS 



Pollen grains are one of the most characteristic elements 

 found in powdered flowers, because they are so small that they 

 are not broken up when the drug is milled. 



The two principal groups of pollen grains are, first, those with 

 non-spiny waHs (Plate 113); and, secondly, those with spiny 

 walls (Plate 114), as shown in the two charts. 



In lavender flowers the pollen grains have six constrictions 

 of the outer wall. This wall is shghtly striated and the cell 

 contents are granular. 



In clover flowers the pollen grains are mostly rounded in 

 outline, the wall is unifomily thickened, and cell contents are 

 coarsely granular. 



In belladonna flowers the pollen grains terminate in three 

 blunt points. 



In Spanish saff"ron the pollen grains are spherical and the 

 cell contents are granular. 



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