214 PLANT ORGANS OR PARTS OF PLANTS. 



PYRETHRI FLORES. INSECT FLOWERS. 



The flowers of several species of Chrysanthemum, nat. 

 ord. CompositcB. 



The product of C. cineraricefolium., Visiani, growing 

 both wild and under cultivation in the mountains of the 

 eastern shores of the Adriatic, and cultivated in Cali- 

 fornia, is called from its -original source Dalmatian insect 

 flowers. C. roseum, Web. and Mohr, and C. carneum, 

 Weber, growing in the Caucasus Mountains and in 

 northern Persia, yield the inferior Persian or Caucasian 

 insect flowers. 



Description. — The flower heads of all three species 

 are hemispherical, from 12 to 20 mm. in diameter with 

 a densely imbricate involucre, naked receptacle, ligulate 

 pistillate ray, tubular perfect disk florets, ribbed fruit, 

 toothed pappus. 



The bracts of the Dalmatian flowers bear slight whitish 

 scarious margins. There are only about 15 ray flowers 

 present, and the achenes are five ribbed. The pappus 

 is about I mm. long. 



The Persian flowers bear brown bordered bracts, 20 

 to 30 rose-red ray florets, and 10 ribbed achenes. The 

 pappus is short, about 0.5 mm. Of the two Persian 

 varieties the rarer product of C. carneum may be 

 distinguished from C. roseum by the paler ray florets, 

 the less pronounced colored bract borders, and by the 

 extending of the anthers outside the corolla tube of the 

 disk florets. The closed flower heads are more valuable 

 than the open ones, as the development of the flower 

 weakens its efficacy as an insecticide. 



Histology. — The upper portion of the stem, which is 

 included with the flowers, bears an epidermis of irregular 

 polygonal cells with numerous stomata, hairs, and 

 glands. The hairs are T-shaped, the long double-pointed 

 horizontal cell often broken off, being supported on a 



