SYMMETRICAL FLOWERS 



37 



the characteristic form and function of all the parts of one kind. P'or 

 the identification of the parts of a typical flower, the few illustratiojis and 

 definitions already given will prove ample, but such flowers are very 

 rare. The great majority of them de\'iate from the tj'pe in one or more 

 directions to such a degree and in such a variety as to very frequently 

 create difficulty in identifying or circumscribing the several parts. To 

 fit the student for properly meeting the difficulties which so arise, as 

 well as for understanding botanical terminology, it is necessary to 

 specify and explain the principal forms of variation and to establish such 

 a classification of them as their varied nature will permit. 



Law 1: Symmetrical Flowers. — The number of parts of each kind or 

 series is the same as of each other, or they have a common multiple. The 

 term Isomerous is used to indicate that the same number of parts enter 

 into the formation of the two or more circles to which the term is appHed. 

 In the case of the gynaecium, it is the carpels which are counted as 

 parts of the circle or series, whether developed each as a se])arate pistil, 

 or all united into one. The number of stamens is normally equal to 

 that of the sepals and petals com})inctl, that is, they form two circles. 

 If the flower is typical, the number of stamens will thus be just twice as 

 great as that of the parts of any other kind. A flower constructed in 

 accordance with this law is called Svmmetrical. 



Fig. 25. Ai>i)ar('iitl.v nioiioniorou.s flowor of I/ippuris. a, raly.\; c, stamen; <i, pistil. 20. Longitu- 

 dinal section of same. 27. Dinierou.s flower of liicuntUa. a, sepals; b, original petals; 6', petal-like 

 bodies developed from one pair of stamens; c, the other pair of stamens, each divided into three; d, 

 pistil; e, eros.s-seetion of ovary, showing two placentae. 28. Trimcrous flower of VercUrutn. 29. 

 Tetramerous flower of Ocnulhcra. 30. Pentamerous flower of Grrauium. 



Terms Indicafin;/ Niuncrical Synivicfri/.— Thus, the flower oi Ilipjniris 

 (Figs. 25 and 2G) has an entire calyx, apparently of one sepal, no corolla, 



