DEVELOPMENT OF PLANTS 



367 



sporophylls become receptive before the anthers open, the flower 

 is said to be protogynous, meaning that the pistil matures first. 

 It must also be borne in mind, although the devices for effecting 

 a crossing are almost universal among the various groups of 

 angiosperms, that there are equally elaborate provisions for the 

 transference of the microspores of perfect flowers to the stigmas 

 of their own flower. This is called autogamy and would appear 

 to be a provision for setting seed in case crossing fails. 



Fig. 263. Development of the perianth: A, inflorescence of Quercus or 

 oak — mi, inflorescence with flowers bearing only microsporophylls; mg, 

 inflorescence with flowers bearing megasporophylls. B, flower of oak, en- 

 larged, consisting of several microsporophylls and a perianth of minute scale- 

 like organs. C, flower of Erythronium or fawn lily. The perianth of six con- 

 spicuous leaf-like organs. D, flower of Melandryum or day pink — ca, calyx of 

 green sepals; c, corolla of five delicate petals. 



From the above discussion we might characterize the primitive 

 flowers as consisting usually of a large and indefinite number of 

 sporophylls, spirally arranged upon the receptacle which is suf- 

 ficiently elongated as to permit the separate attachment of each 

 organ. Following the development of this type of flower, there 

 appeared as the next advance, minute outgrowths about the 



