SPERM VFOPHYTES 255 



is poorly expressed in the terms synsepalous, sympetalous, monadelphous, 

 and syncarpous. The syncarpous condition (syncarpy) is extremely 

 common (fig. 568); but the sympetalous condition (sympetaly) is note- 

 worthy as giving name to one of the three divisions of angiosperms. 



All such terms as "united," "fused," " coalescent," and their technical equiva- 

 lents suggest a very wrong impression as to the origin of the structure concerned. 

 The separate parts implied in the words " united," etc., never had a separate 

 existence. For example, in many cases separate petals occur ; and where there 

 is zonal development they are not separate, but this does not mean that they 

 have " united " or " coalesced." 



Hypogyny to epigyny. — Zonal development often involves more than 

 a single set. In sympetaly the stamen zone is also usually involved, so 



Figs. 569-571. — Diagrams to show structure of hypogynous (569), perigynous 

 (570), and epigynous (571) flowers. — After Ganong. 



that the stamens seem to arise from the tube of the corolla (fig. 564). 

 There are three conditions in reference to zonal development that in- 

 cludes more than one set which are important to note, for they have to 

 do with a distinct evolutionary tendency of the flowers. The most 

 primitive condition is one in which the sets are entirely free from one 

 another (unless it be the corolla and stamens), in which case the flower 

 is hypogynous, meaning that the three outer sets arise from beneath the 

 carpel set (fig. 569). In another condition, zonal development involves 

 the three outer sets, resulting in an urnlike structure surrounding 

 the carpels, from the rim of which the distinct sepals, petals, and 

 stamens arise. In this case the flower is perigynous, meaning that the 

 three outer sets seem to arise around the carpel set (fig. 570). In the 

 last condition the zonal development involves all of the sets, leaving a 

 cavity in the center, so that all of the sets seem to arise from the top of 

 the ovary. In this case the flower is epigynous, meaning that the floral 

 members seem to stand upon the ovary (fig. 571). Epigyny is regarded 



