106 THE CALYX AND COROLLA. [LESSON 15. 



(Fig. 210), Toad-Flax (Fig. 211), Dead-Nettie (Fig. 209), Catnip, 

 Horsemint, &c. ; and in the Sage, the Catalpa, &c., the calyx also is 

 two-lipped. This is owing to unequal union of the different parts of 

 the same sort, as well as to diversity of shape. In the corolla two 

 of the petals grow together higher than the rest, sometimes to the 

 very top, and form the upper lip, and the three remaining ones join 

 on the other side of the flower to form the lower lip, which therefore 

 is more or less three-lobed, while the upper lip is at most only two- 

 lobed. And if the calyx is also two-lipped, as in the Sage, since 

 the parts of the calyx always alternate with those of the corolla 

 (247), then the upper lip has three lobes or teeth, namely, is com- 

 posed of three sepals united, while the lower has only two ; which is 

 the reverse of the arrangement in the corolla. So that all these 

 flowers are really constructed on the plan of five, and not on that of 

 two, as one would at first be apt to suppose. In Gerardia, &c. (Fig. 

 194, 195), the number five is evident in the calyx and corolla, but is 

 more or less obscured in the stamens (249). In Catalpa this num- 

 ber is masked in the calyx by irregular union, and in the stamens by 

 abortion. A different kind of irregular flower is seen in 



277. The Ligulate or strap- 

 shaped corolla of most com- 

 pound flowers. What was 

 called the compound flower 

 of a Dandelion, Succory (Fig. 

 221), Thistle, Sunflower, As- 

 ter, Whiteweed, &c., consists 

 of many distinct blossoms, 

 closely crowded together into 

 a head, and surrounded by an involucre (208). People who are not 

 botanists commonly take the whole for one flower, the involucre for 

 a calyx, and corollas of the outer or of all the flowers as petals. 

 And this is a very natural mistake when the flowers around the 

 edge have flat and open or strap-shaped corollas, while the rest 

 are regular and tubular, but small, as in the Whiteweed, Sunflower, 

 &c. Fig. 219 represents such a case in a Coreopsis, with the 

 head, or so-called compound flower, cut through ; and in Fig. 220 

 we see one of the perfect flowers of the centre or disk, with a reg- 

 ular tubular corolla (a), and with the slender bract (#) from whose 



FIG. 219. Head of flowers (the so-called " compound flower ") of Coreopsis, divided 

 lengthwise. 



