2G THE STRUCTUEE OF FLOWEES. 



there is no doubt but that similar processes will account for 

 one stamen as for one petal. Thus Eippuris with one, is 

 allied to Myriophyllum with four ; while Centranthus has one, 

 Fedia has two and Valeriana three. 



Casuarina alone seems to raise a doubt of its being 

 degraded and possibly a primitive form ; but this is solely 

 because it has no living allies (excepting perhaps Mynca). 

 The terminal stamen would not be of itself a point of 

 importance, as it has a parallel in Euphorbia ; but it is its 

 isolation without afiSnities, its peculiar equisetum-like habit, 

 which seem to indicate great antiquity, so that no inference 

 can fairly be drawn to interpret its present monandrous 

 condition. 



Amongst Monocotyledons, Canna is clearly monandrous 

 by petalody of the other stamens. Orchis by metamorphosis 

 also. Lastly, Naias, Gaulinia, Zostera, Zannich£ell/3,, and Lemna 

 are in all probability greatly degraded forms' from higher 

 plants, degradations being the usual effect of an aquatic life, 

 and not primitive types of Monocotyledons. 



One carpel is not at all uncommon, as in the Leguminosa. 

 As Affonsea has five, the absence of four in this order is no 

 doubt due to arrest. In the tribe Berbereoe, however (if my 

 interpretation be correct, of the origin of the seven whorls 

 of three each constituting the flowers of Berberis, as explained 

 below), the one carpel may be the last of an originally 

 \ \ continuous spiral, formed from eleven pairs of opposite leaves, 

 ' ' now broken up into seven ternary whorls, with one over. It 

 may, however, be the remaining one of three, which possibly 

 constitutes a ternary gyncecial whorl, which is characteristic 

 of the tribe LardizdbalecB of the same order Berberideoe. 



Dimerous Whorls. — A dimerous arrangement is not par- 

 ticularly common, though a quaternary calyx is dimerous in 

 its development, as the sepals emerge from the axis in sue- 



