168 BOTANY. [CHAP. v. 



in reality the flower with an inferior ovary is a modi- 

 fication or evolution from the earlier type where the 

 ovary is superior. A transition stage, where the nor- 

 mally inferior whorls sepals, petals, and stamens have 

 only crept halfway up the ovary before becoming free 

 from it, is seen in some of the saxifrages, houseleeks, etc. 

 The appearance of the ovary when mature that is, the 

 fruit is in many instances so widely different from the 

 ordinary conception of a leaf-like structure, that unless 

 the transitional phases are indicated, it would be difficult 

 to realize the fact that the carpels or components of the 

 ovary are in reality modified organs originating, and, in 

 the early stage, presenting the characters peculiar to 

 leaves. This idea will be made clear by the examination 

 of the pod of a common pea, which is a carpel or leaf folded 

 so that its two edges meet and grow together, thus 

 forming a closed cavity, the ovary. The tip of the 

 carpellary leaf forms the stigma, and the ovules or young 

 seeds spring from the two margins of the carpel and 

 grow into the cavity formed by the closed-up carpel. In 

 the pea a single carpel constitutes the fruit, but in most 

 instances the fruit is composed of more than one carpel. 

 The fruit of the marsh marigold (Oaltha palustris) con- 

 sists of a number of carpels which, like that of the pea, 

 still remain comparatively unchanged and present a leaf- 

 like appearance ; and as these carpels remain free from 

 each other, the fruit, which consists collectively of all the 

 carpels belonging to one flower, is apocarpous. The 

 syncarpous ovary, on the contrary, is composed of two, 

 or generally more, carpels arranged in a whorl and 

 grown to each other by their edges. The number of 

 carpels forming a syncarpous ovary is in many cases 



