DEVELOPMENT OF PLANTS 



485 



alliance, we find a very natural sequence leading to the higher 

 families. For example the lower members of the bell-flower 

 family have nearly or quite regular flowers, parts in five, anthers 

 grouped about the style but not united, fruit a capsule with many 

 seeds as in the harebell {Campanula) and Specularia (Fig. 337, 

 A, C). In the Lobelia the corolla usually becomes irregular 

 and slit down one side, thus approaching the form assumed in 

 the highest groups of the order. The anthers arc united about 

 the style which is two lobed and provided with a whorl of hairs 

 to sweep the spores from the cylinder of anthers. The fruit is 

 a capsule of two carpels (Fig. 337, D-E). This brings us to 

 that great group of familiar plants that were formerly known as 

 the Compositae, but that are now separated into the chicory 

 family (Cichoriaceae) of 1,400 species, the ragweed family 

 (Ambrosiaceae) of 55 species, and the thistle family (Cardu- 

 aceae) of over 11,000 species. The most conspicuous feature 

 of these three families is the aggregation of numerous small 



I 



Fig. 338. Habit of the dandelion (Taraxacum), an example of the Cicho- 

 raceae: a, appearance of the inflorescence or head; b, appearance of the head 

 during the ripening of the seed; in, involucre; c, appearance of the fruit. 



