28 BULLETIN 824^ U. S. DEPARTMENT OF AGRICULTURE. 



many of which were elongated, having oblique or pointed ends and 

 being joined in the manner of prosenchyma cells. These were usually 

 found as fragments in the powder, and could be recognized by their 

 walls pierced with narrow canals. He also observed these fragments 

 to be much more numerous in the Persian than in the Dalmatian 

 powder. He explained this by the fact that the greater portion of 

 the very rigid, greenish, involucral scales (with the exception of the 

 dark, reddish-brown scarious margin) consisted of sclerenchyma cells. 

 Numerous hairs of a very characteristic structure were found on the 

 outer surface and along the membranous edges of the scales of the 

 Dalmatian flowers and on the flower stems as well. Each of these 

 hairs consisted of a long cell with attenuated ends, placed horizontally 

 on a 1 to 3 celled stalk arising from the epidermis. The terminal hori- 

 zontal cell was bent and twisted in various ways, rather hooked at the 

 end and forming feltlike layers, especially on the outermost scales. 

 ' Schrenk detected few hairs in the Persian flower insect powder 

 which he examined. The flowers of CTirysantJiemum roseum which 

 he subsequently examined were almost entirely glabrous, with the 

 exception of the hairs found where the stem widens into the recep- 

 tacle, as well as at the base of the outermost scales. The hairs were 

 of the same structure as those found on Chrysanthemum cinerarise- 

 folium, only the terminal cells were much longer. He considered the 

 papillse covering the upper epidermis the most conspicuous among the 

 fragments of the marginal corolla. These were not regarded as 

 diagnostic, since the petals of other related species are similarly con- 

 structed. Stomata were remarkably numerous on the lower side of 

 the marginal corolla. He did not find the insect flowers raised in 

 California (Buhach), which belong to Chrysanthemum cinerarise.- 

 folium, any different in structure from flowers grown in their native 

 coimtry. 



Ejrkby (156) and Verneau (285) have called attention to one dis- 

 tinction which they believed might aid in identifying the Persian 

 powder. They found the papiUae of the ray florets to be larger than 

 those of the Dalmatian florets, thickened somewhat more at the apex, 

 and with sides making a wider angle. Malfatti (186) has gone into 

 the description of the Caucasian (Chrysanthemum roseum) flowers 

 quite extensively, figuring the various parts of the flower head. 

 Siedler (258) describes the physical characteristics of powders made 

 from different parts of the flower. 



Microscopic Examination op Insect Powder. 



Before attempting the critical examination of a commercial insect 

 powder, the microscopist should become thorouglily familiar with 

 the various parts of the insect flower head, in the whole as well as 

 in the powdered condition. It has been found advantageous to sep- 



