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INTRODUCTION 
genera here associated present a great variety in appearance and 
in structure, and the untrained observer might wonder on what 
grounds they were brought together, especially when compared 
with such Orders as the Cruciferae, the Umbelliferae and others. 
Thus the genera Clematis, Anemone and Caltha have a calyx and 
no corolla ; but the sepals are usually brightly coloured and are 
commonly called petals. Their true nature is deduced from 
analogies, the occasional presence of rudimentary petals and other 
circumstances. In Delphinium and Aconitum the sepals and petals 
are so peculiarly formed that it is difficult to decide which belong 
to the former and which to the latter series. Actcea, again, differs 
from all the other genera in having a berry fruit. In this connec- 
tion it must be conceded that a Ranunculus is much more like a 
Potentilla than any of the genera named ; but the essential differ- 
ence is that the stamens are inserted on the calyx in Potentilla, 
whereas in Ranunculus the sepals may be pulled away leaving the 
stamens on the receptacle. 
A few other examples of unusual structures or developments 
in flower and fruit may be useful. 
In Schizandra (Magnoliaceae) the receptacle or axis on which 
the carpels are seated elongates in the fruiting condition to six or 
nine inches, and has the appearance of being the axis of a raceme 
of flowers, each containing a single carpel. 
In the Papaveraceae the sepals fall so early that the expanded 
flower consists of petals only, enclosing the stamens and pistil. 
In the Polygalaceae two of the sepals are like petals and the 
lowest of the three petals is much enlarged and crested. 
In the Malvaceae the petals are often slightly connate at the 
base and adnate to the staminal column. 
In Impatiens the lower sepal (or three combined) is the largest 
and most conspicuous part of the flower. 
In Helinus (Rhamnaceae) the ovary is inferior. 
In Coriaria the petals are persistent, become fleshy and enclose 
the carpels. 
In Bryophyllum and Kalanchoe (Crassulaceae) the petals are 
united, forming a gamopetalous corolla. 
The same thing occurs in the Cucurbitaceae. 
In Cornus capitata the white bracts of the involucre, enclosing 
a cluster of small flowers, resemble the sepals of a Clematis. 
In the Asclepiadaceae the structure of the stamens is very 
peculiar, and the pollen coheres in masses similar to the condition 
in orchids. 
In Euphorbia several male flowers surround one female flower, 
