35Q 



EVOLUTION OF THE FLOWER 



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

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



Following the development of the type of flower noted in the 

 cat-tail and willow, there appeared as the next advance in the 

 flower, minute outgrowths about the sporophylls, known as the 

 perianth. In its simplest form this consists of a few scales as 

 in the sweet flag, oak, etc. (Fig. 263, B), but in higher forms, 



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

 oak — mi, inflorescence with flowers hearing 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 conspicuous leaf-like organs. D, flower of Melandryum or day pink 

 — ca, calyx of green sepals ; c, corolla of five delicate petals. 



the perianth appears as the conspicuous leafy portion of the flower 

 as in the lily (Fig. 263, C). Finally flowers appear in which 

 the leaves of the perianth become differentiated into an outer 

 calyx composed of several green sepals and a corolla of larger, 

 more delicate and often brightly-colored leaves, called the petals 

 (Fig. 263, D). We have now reached a point where the flower 



