10 BULLETIN 795, U. S. DEPARTMENT OP AGRICULTURE. 



ei's and fioin daisy flowers has enipliasized the need for cantion in 

 placing- reliance upon any histological characters in the daisj^ flow- 

 ers other than those of the achene. Other characters, with the ex- 

 ception of the T-shaped hairs of the Dalmatian flowers (PI. II, fig. 

 3) and the ciTstal-bearing stone cells of the achene, are too nearly 

 like similar characters in insect flowers. While these hairs and crystal- 

 bearing stone cells of the achene would furnish a means of iden- 

 tifying Dalmatian flowers in a mixture with other materials, they very 

 apparently offer no means of discovering the presence of the daisy 

 flowers when mixed with Dalmatian flowers. Thus the presence of 

 this brownish-red material (PI. I, fig. 4) and the palisade-like epi- 

 dermal cells (PI. II, fig. 2) furnishes a reliable means of detecting 

 even small quantities of dais}^ flowers in a mixture. 



No attempt has been made to describe the other parts of the daisy 

 floAver in detail, the scope of this pai)er being limited to those difl'er- 

 entiating tissue elements which might be readily detected in an 

 insect powder adulterated with powdered daisy flowers. A brief de- 

 scription of the diagnostic tissues of the achenes of the Dalmatian 

 flower (C. ciiierariafoTutin) and of the daisy flower (C. Lettcaiithe- 

 iJUiDi) follows: 



Dalmatian foicer achene. — Characterized in the powder by rec- 

 tangular patches of hard sclerenchyma tissues, strongly lignified a'nd 

 possessing numerous clinorhombic crystals which exhibit a great 

 variety of colors under polarized light. In older flowers (open flowers) 

 isolated stone cells are very common (PI. I, fig. 3; PL II, fig. 1). 



Daisy floicer achene. — Characterized in the powder by irregular 

 dark-red fragments of variable size exhibiting a very deep-red color 

 when the powder, after heating in chloral hydrate solution (about 

 1:1), is examined under the microscope; also by closely-packed pal- 

 isade-like tissue Avith thick walls and narrow lumina, usually present 

 in radial section in the powder (PI. I, fig. I; PI. II, fig. 2). 



SUMMARY. 



While there are certain differences in the chemical composition of 

 Chri/santheniitm ciiierariafaJiiDn and Chrijsaiiiltemiiin Leiicanthemum, 

 a chemical analysis is insufficient to shoAv adulteration of insect pow- 

 der with daisA' flowers. 



Adulteration of insect powder Avith ]»oAvdered daisy floAAers can be 

 definitely determined by microscopic examination. PoAvdered daisA' 

 fioAA^ers are distinguished by (a) the irregular dark-red fragments of 

 the achene, and (b) the palisade-like cells comprising the costal tissue 

 of the achene. 



