78 FLOWERS 



INSECT FLOWERS (Dalmatian) 

 (Flores Pyrethri, Pyrethrum Flowers) 



Source, &C. Dalmatian insect flowers are the unexpanded flower- 

 heads of Chrysanthemum cineraria folium, Visiani (N.O. Composite), 

 a native of Dalmatia, Herzegovina, and Montenegro, and cultivated 

 there as well as in Japan and California. 



The flowers of several composite plants have long been known to 

 possess the remarkable property of stupefying flies and other small 

 insects. None, however, appears to act so energetically as insect 

 flowers, and these are most active if collected when they are fully 

 developed, but before they expand. They are then known com- 

 mercially as ' closed ' flowers, c half-closed ' and ' open ' flowers 

 being collected at more advanced stages of development. They retain 

 their insecticidal properties indefinitely, even in the state of dry powder. 

 The leaves have been shown to be destitute of insecticidal properties. 



Description. The closed flowerheads of commerce are of a dull 

 brownish yellow or greyish brown colour and about 10 mm. in diameter. 

 The bracts of the involucre, which are arranged in two or three rows, 

 are yellowish or greyish in colour, lanceolate, hairy, and membranous 

 at the margin. In the closed flowers they are erect, but as the flowers 

 expand they bend outwards, the capitulum assuming a flattened 

 hemispherical shape. There is only one row of ray-florets, with 

 brownish or whitish ligulate corollas. The disc-florets, which are 

 numerous, have comparatively short yellow corollas. The fruit is 

 longer than the corolla, club-shaped, and provided with five ribs that 

 project so strongly as to make it appear almost winged. Both the 

 corolla and the fruit are sprinkled with yellow shining oil-glands. 

 After the corolla has been removed, the calyx may be seen in the 

 form of a raised membranous ring crowning the fruit. The receptacle 

 is naked and nearly flat. 



' Closed ' flowers are sub-globular or sub-conical in shape, and 

 usually bear the yellowish, shrivelled, ligulate corollas ; ' half-closed ' 

 flowers are nearly hemispherical in shape, and the corollas of the 

 ray-florets are more spreading ; ' open ' flowers are still flatter, and 

 most of the ligulate corollas have been broken off ; they are often 

 devoid of the tubular corollas of the disc-florets also, and then present 

 a reticulated appearance due to the membranous calices crowning 

 the closely packed fruits. 



Insect flowers possess a bitter, acrid taste ; the odour is aromatic, 

 but not strong. 



The student should observe 



(a) The sub-globular or sub-conical shape of the ' closed ' flowers, 



(b) The yellowish colour of the bracts, 



