168 POWDERED VEGETABLE DRUGS 



make percentage determinations; likewise of senna pods and of senna 

 leaflets. 



4. Insect Powder. Secure samples of pure flower heads of the 

 three species of pyrethrum (Chrysanthemum roseum, C. Marshalli 

 and C. androsoemifolium), both the fully expanded flower heads and 

 the partially expanded heads, making six samples. The thoroughly 

 dried flower heads are reduced to a No. 80 powder and the counts are 

 made of the pollen grains (mature and immature) and of the groups 

 of the sclerenchyma cells and also of the groups of fibrous tissue. The 

 trichomes and the somewhat papillose epidermal cells have a diagnostic 

 significance only. The counts thus obtained should be carefully 

 made and the results recorded for future reference and use. 



Prepare a powder of the stems of one of the species of insect flower 

 and make a careful count of the groups of the fibrous tissue present. A 

 few pollen grains will also be noted. The count of the groups of 

 fibrous tissue represents a 100 per cent, stem tissue. Now make ad- 

 mixtures of pure insect powder and pure stem tissue, and from a count 

 of pollen as well as of the stem tissue, acertain the amount of the 

 several admixtures. A whole series of problems will suggest them- 

 selves and should be tried out as time and opportunity will permit. 

 The sclerenchyma group count and mature pollen grain count will 

 indicate the percentage amount of mature flower, heads used. What 

 is the number of pollen grains per gram in a 100 per cent, insect 

 powder? 



5. Digitalis Leaves. Secure samples of the leaves from the first 

 year plants, and from the second year plants at the time of flowering. 

 Dry, powder and prepare for the count as the above samples. Make 

 counts of the simple trichomes. In the first year plants the leaves 

 will show fewer trichomes. What are the total trichomatic counts 

 for the first year leaf and for the second year leaf? Also make a 

 count of the groups of fibrous tissue in the two samples of leaf. 



Prepare samples of digitalis stems and make counts of the trichomes 

 and of the groups of fibrous tissue. Make fifty to fifty admixtures of 

 digitalis leaf and of digitalis stem and redetermine the amount of 

 leaf and of stem respectively, based upon the trichome count and also 

 upon the count of the groups of fibrous tissue. 



Digitalis leaf (in the powdered form) is identified by the simple 

 and the glandular trichomes. The cells of the simple trichomes are 

 more or less collapsed, usually one cell is flattened in one plane, the cell 

 following being collapsed in a plane at right angles to that of the 

 other. The glandular trichomes usually bear two terminal secreting 

 cells. In making the counts of the trichomes, all trichomatic frag- 



