68 PART I. ORGANOGRAPHY. 



4 



regularity is the exception and not the rule, and there is no 

 known member of the family of Orchids that is not very irregular. 

 Fig. 204 represents the irregular flower of Monk's-hood or 

 Aconite. In the outer whorl there are five sepals, the upper of 

 which is hooded, and the two lateral ones differ from the two 

 lower in size and shape. From the second whorl, or corolla, all 

 but two pieces are wanting, and these, though really petals, bear 

 little resemblance to ordinary ones in shape, a shows the flower 

 as it appears naturally, and c represents the same with the parts 

 of the calyx and corolla separated, showing their shape and 

 relations. 



(5) Deviations due to the Union of Parts. There is perhaps 

 nothing which contributes so much to obscure the plan of the 

 flower and cause deviations from the typical form as this. 



The growing together may take place in two ways. Either 

 the parts of the same whorl may coalesce partly or wholly, or 

 parts of different whorls may become more or less united. The 

 former is termed cohesion, the latter adhesion or adnation. Cohe- 

 sion, either complete or partial, may take place between the 

 members of any set of floral organs, and any two sets may adhere 

 partly or wholly. Even organs so different in their functions as 

 stamens and pistils not infrequently become united, as in the 

 Orchis family. 



Practical Exercises. 



Examine flowers of the following plants : The Tiger Lily, the house 

 Geranium, the Morning-glory, the Butter-cup, and the Rose, and determine, 

 (1) the numerical plan of each flower, (2) draw a ground plan of each, repre- 

 senting, as in Figs. 195 and 203, the number and relation of parts, and note in 

 each what deviations from the typical flower occur. 



