460 



THE POLEMONIALES 



(Limnanthemum) and the highly specialized plants of the dog- 

 bane and milkweed families. The latter family is distinguished 

 by the microspores being united into club-shaped pollinia that 

 are attached, one from each of the two adjoining anthers, to a 

 peculiar hook, so that the leg of the insect becomes caught in 

 the hook and withdraws the pollinia in pairs. 



Fig. 329. 



Fig. 330. 



Fig. 329. Flower of the morning-glory (Ipomoea), showing the tubular 

 corolla characteristic of the Polemoniales. 



Fig. 330. Boraginaceae: C, inflorescence of comlrey (Symphytum). Note 

 the coiled inflorescence, a, a feature of this family. D, section of flower, 

 showing the deeply four-lobed ovary and the stamens cohering high on the 

 corolla and alternating with small tongue-like scales. 



152. Polemoniales, or Phlox Order. — This group is the richest 

 in the number of species, over 14,600, of any order of angio- 

 sperms. The advance over previous orders is seen in the more 

 complete adhesion of corolla and stamens, the filaments appear- 

 ing to rise at a higher point on the corolla (Fig. 330, D) and 

 the stamens are reduced to a single whorl, and frequently less 

 than five in number. The pistils cohere completely and are 

 usually composed of but two carpels. This reduction is asso- 

 ciated with a pronounced irregularity of the corolla in the higher 



