THE SUNFLOWER FAMILY 385 



(Lobelia) affords a case of partial coalescence somewhat dif- 

 ferent from any of our foregoing examples. The two upper- 

 most petals are entirely free from one another, though coal- 

 esced with the side ones, and these with the lowest, so that 

 all five petals are as if united into a tube which is split down 

 the back.' 



In bellflowers (Campanula) the more or less bell-hke corolla 

 from which they take their name shows no irregularitj'. 



M 0.311]/ herbs with milky juice; flowers solitary or loosely 

 clustered, perfect, regular or irregular, mostly gamopetalous; 

 stamens five, free or monadelphous and syngenesious; the pollen- 

 sacs straight; ovary inferior with two to five axile placentre; fruit 

 capsular. 



139. The sunflower family (Compositae) . Examples: 

 Jerusalem artichoke (Figs. 59 I-IV, pages 61, 62), lettuce 

 (Figs. 75-77, pages 72-74), and wormwood (Fig. 155, page 

 160). 



Formulas of Helianthus, Lactuca, Artemesia, and CompositEe 

 arc given on pages 420, 421. 



More than a tenth of all the species of flowering plants 

 belong to this the largest family of seedworts. The very 

 characteristic inflorescence is sometimes mistaken for a single 

 flower, and was indeed called a "compound flower" by the 

 earlj' botanists. In reality, as will be readily seen, the small 

 flowers are borne on a more or less flattened expansion of 

 the peduncle, called the receptacle, and form a compact head 

 surrounded by an involucre of bracts resembling sepals. As 

 if to increase the deception the outer row of florets often have 

 what are called strap-shaped corollas formed by a coalescence 

 of the petals into one flat piece (Fig. 59 II, III), somewhat as 

 in the Indian tobacco but more complete; and these corollas 

 radiate so as to look like petals. The inner part of the head 

 in such cases as the sunflower is made up of regular florets 

 (Fig. 59 III). Many members of the family have only regu- 

 lar florets, while still others have all the florets strap-shaped 

 or sometimes labiate. 



The calyx may consist of a few papery scales, or of nimier- 



1 This condition is indicated in the formulas by P" 5). 



