7i8 A TEXT-BOOK OF BOTANY. 



tubular flowers, the bristles of this series being erect and with 

 the outer spreading. 



Calendula officinalis (Marigold) is an annual herb with alter- 

 nate, spatulate, oblanceolate, entire or serrate leaves. The flowers 

 are yellow and form solitary heads, consisting of both ray and 

 tubular florets. In the cultivated varieties most of the tubular 

 florets are changed to ligulate, the latter being official (Fig. 227). 



While the Compositae include a large number of genera and 

 species, the plants do not yield many important drugs, although a 

 number are used in medicine and for other purposes. 



The so-called Insect Flowers {Pyrethri F lores) are the 

 partly expanded flower-heads of several species of Chrysanthe- 

 mum, and are used in the preparation of a powder which is a 

 powerful insecticide. The plants are perennial herbs resembling 

 in their habits the common white daisy (C. Lcucanthetnum) . The 

 Dalmatian Insect Flowers are obtained from C. cineraricc folium, 

 growing in Dalmatia, and cultivated in Northern Africa, Cali- 

 fornia and New York. The heads as they occur in the market 

 are about 12 mrh. broad, light yellowish-brown and have a slightly 

 rounded or conical torus, which is about 12 mm. in diameter and 

 consists of 2 or 3 series of lanceolate involucral scales. The ray- 

 florets are pistillate, the corolla varying in length from i to 2 cm. 

 and having numerous delicate veins and 3 short, obtuse or rounded 

 teeth. The tubular flowers are perfect and about 6 mm. long. The 

 ovary is 5-ribbed and the pappus forms a short, toothed crown. 

 The odor is distinct and the taste bitter. 



Persian Insect Flowers are derived from C. roseum and C. 

 Marschallii, growing in the Caucasus region, Armenia and North- 

 ern Persia. The heads are about the size of those of C. cinerarice- 

 foliiim; the torus is dark brown ; the involucral scales and ray- 

 florets are purplish-red ; the ovary is lo-ribbed. 



Insect flowers contain from a trace to 0.5 per cent, of a vola- 

 tile oil, the Persian flowers containing the larger proportion, and 

 the amount decreasing with the maturing of the flowers. They 

 also contain two resins, varying from 4 to 7 per cent., the larger 

 amount being found in the Dalmatian flowers ; a small quantity 

 of a glucoside and a volatile acid. 



The principle toxic to insects is Pyrethron, an amber-yellow, 



