470 THE CAMPANULALES 



14,500 species are known. The parts of the epigynous flowers 

 are arranged in four whorls of usually five members each. The 

 anthers are aggregated and usually cohere, forming a sheath 

 about the style which is frequently covered with hairs and acts 

 like a piston rod in the cylinder of anthers. The flowers are 

 protandrous with few exceptions, the anthers opening on their 

 inner sides and discharging the spores upon the style which later 

 sweeps them out as it elongates. The pistils are generally re- 

 duced to a single one-ovuled carpel that ripens as an akene. 

 Leaving out of consideration the gourds which include the 

 melons, pumpkins, cucumber and gourd, as a family of uncertain 

 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 Speciilaria (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 are 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 

 flowers in heads subtended by one or more rows of bracts that 

 form a calyx-like involucre (Fig. 338, in). This type of in- 

 florescence might readily be mistaken for a single flower as the 

 buttercup, rose, etc. ' This tendency to group the flowers in 

 heads and compact clusters has been attained in several orders, 

 notably the mustards, peas, Umbelliferae, mints, scrophularias, 

 and especially in the teasel family, page 468. But in no group 

 has the aggregation been so successful and coupled with such 

 efficient types of flowers. Leaving out of consideration the de- 



