364 BOTANY: PRINCIPLES AND PROBLEMS 



order marks the highest point of development among the 

 Archichlamydeae. 



The following orders are most important among the Sympetalae : 



Ericales (Fig. 109). — These are the heaths, mountain laurels, 

 blueberries, and their allies, most of them shrubby plants, 

 including many evergreens. The order is intermediate, in 

 certain of its characters, between Archichlamydeae and 

 Sympetalae. 



Tubiflorales (Fig. 104). — Here are placed the morning-glory, 

 phlox, borage, verbena, nightshade, mint, and figwort families 

 and a number of others, most of the members of which are herbs. 

 The corollas are conspicuous and prevailingly tubular, and are 

 regular in the lower families but extremely irregular in the higher 

 ones. The order comprises not only many of our garden flowers 

 but a number of such important crop plants as the potato and 

 tobacco. 



Ruhiales (Fig. 236). — Here are the madder and honeysuckle 

 families, which are prevailingly trees and shrubs, although 

 herbaceous species also occur among them. The flowers are 

 most commonly on the plan of four and tend to be grouped in 

 compact clusters. 



Campanulales (Fig. 239). — This order includes the gourd, 

 bellwort, and composite families, most of the members of which 

 are herbaceous. The last is the largest and most widespread 

 family among angiosperms. Its flowers are arranged in complex 

 heads, each of which somewhat resembles a single flower, the 

 flowers at the margin of the head often being different from 

 those in the center. The calyx is greatly reduced and becomes a 

 scalelike pappus surmounting a single-seeded ovary. This 

 family is a remarkably successful one and marks the highest point 

 in evolutionary advance among the dicotyledons. 



Monocotyledoneae or Monocotyledons. — These plants, of 

 which there are some 30,000 species, are characterized by the 

 possession of a single cotyledon in the embryo, closed or parallel 

 venation in the leaf, scattered vascular bundles in the stem, and 

 a floral plan based on multiples of three. The group probably 

 arose from somewhere among the primitive dicotyledons and 

 its evolutionary advance has been more or less parallel with 

 that of the latter group. With the exception of one order, 

 monocotyledons are all herbs. Among the important orders 

 are the following: 



