DEVELOPMENT OF PLANTS 



475 



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

 prolonged mass growth of the corolla and stamens, the filaments 

 appearing 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 are completely compound and 

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



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 comfrey {Symphytum). Note 

 the coiled inflorescence, u, 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. 



ciated with a pronounced irregularity of the corolla in the higher 

 families and a high degree of specialization in the construction 

 of the flower which in part accounts for the occurrence of the large 

 number of individuals. The order is noted for its great number 

 of showy flowers and the large tubular corollas which attain their 

 highest perfection in several of the families. 



{a) The More Important Families of the Phlox Order. — ^The 

 flowers of the lower families are regular, as in the morning- 

 glory, sweet potato, dodder (Cuscuta), a yellow thread-like para- 



