MICROSCOPICAL EXAMINATION OF POWDERED VEGETABLE DRUGS 87 



The pollen grains of different flowers from the same family or order 

 usually resemble each other quite closely. Pollen grains may cling 

 to any part of the flower, and are even found with pistillate flowers 

 (Cannabis Indica, brayera). The number of pollen grains is rarely 

 diagnostic. If considerable pollen is found with what are supposed to 

 be pistillate flowers, as Indian hemp, brayera and Crocus, it may indi- 

 cate adulteration. Occasionally the number of pollen grains is indica- 

 tive of the quality and purity of the article, as in insect powder (Pyre- 

 thrum) . 



2. Pistillate Elements. These are not characteristic or diagnostic. 

 The cells are usually parenchymatous, small and thin-walled. 



3. Petals. Note the epidermal elements and compare with those 

 of the leaf. Stomata are usually fewer in number and less distinct 

 and the epidermal cells are less characteristic. Trichomes are less 

 common, but very diagnostic. The epidermal cells may contain 

 diagnostic coloring matter. Parenchyma and vascular tissue usually 

 deficient and not important. 



4. Sepals. 'The tissue elements and cell-contents of sepals are in 

 all respects similar to those of the leaf. 



5. Pappus. These structures are present in many flowers (Com- 

 ^ositsB) and quite important, though closely similar in different species. 



6. Stone-Cells or Sclerenchyma. These elements are often found. 

 They may be derived from the torus (receptacle), or, in the case of 

 highly matured flowers, from the seeds, and are generally highly 

 diagnostic. 



To sum up briefly, the important diagnostic elements of flowers are 

 pollen grains, trichomatic structures, cell-contents and occasionally 

 stone-cells. Vascular elements are not very abundant nor especially 

 characteristic. Parenchymatous tissue is quite typical and quite free 

 from starch and other storage substances. Resin and other secondary 

 products may be present. The student should keep in mind whether 

 a part (as petals, carolla without calyx, etc.) or the entire flower is used. 



3. FRUITS AND SEEDS 



Fruits and seeds are placed in one group. The terms fruit and seed 

 are very loosely applied; in one instance it refers to a fruit (fennel, 

 caraway, coriander, etc.), again to the flower (Artemisia); in other 

 instances the term fruit or seed is applied, not to the whole organ, 

 but to a part, as in peeled colocynth, decorticated pepper, etc. 



1. Epidermal Elements. Those of the pericarp are, in many in- 

 stances, similar to those of leaf or stem, and such a comparison should 

 be kept in mind. Trichomes are usually non-glandular and diagnostic. 



