DEVELOPMENT OF PLANTS 



395 



the calyx and corolla become more or less tubular and the carpels 

 unite, forming a compound ovary. The cohesion of the organs 

 is often associated with other variations of the flower. Among 

 the more common of these changes is the adhesion of the stamens 

 to the corolla, which is usually associated with the basal growth 



FIG. 296. Structure of dicotyledonous seeds: A, nearly mature seed of 

 Lepidium. The embryo consists of the hypocotyl, hy, ending below in the 

 root, r, and the root cap and above in the epicotyl or plumule, pi. Two 

 cotyledons, c, arise laterally from the stem ; /, f uniculus ; mi, micropyle ; in, 

 integuments; en, remains of endosperm. B, section of seed of water lily 

 e, embryo with two cotyledons attached laterally to the minute stem of 

 the embryo and surrounded by a layer of endosperm cells; mg, sporangial 

 cells or perisperm ; i, integument. 



of the receptacle, forming the perigynous type of flower, and the 

 adhesion of the receptacle to the ovary so that the perianth and 

 stamens apparently arise from the top of the ovary, epigynous 

 type of flower (page 353). The irregularity that characterizes 

 the highest types of flowers in many of the orders is the most 

 helpful of all these variations, as is indicated by the abundance 

 and more common occurrence of such forms. 



The most characteristic feature of the dicotyledons is the 



