I 



I 



DICOTYLEDONS. 647 



Berberis, 6*3+3 ^3+s ^^4+3 ^'i, 

 Podophyllum, S, P,^i St,\, C,. 

 Cruciferse, ^'2+2 Pxi 'S'4+2' C^^^^y 



A large number of examples of this general formula are afforded by the 

 family Menispermaceae, in which the whorls are sometimes dimerous, sometimes 

 trimerous, while sometimes whorls of each description occur in one flower; and 

 where almost every one of the organs may disappear by abortion ^ 



In addition to the trimerous flowers already mentioned, there are also some 

 which come under the first-mentioned general formula '5'„/'„ ^/„(+„) Q(_„,) ; as, 

 for example, Rheum with the formula S^ P^ St^^^ Cy Other trimerous flowers 

 again appear to belong to a third type, as Asarum with the formula .^3 St^^^ C^. 



When the number of staminal whorls is considerably increased, it not unfre- 

 quently happens that the number of stamens in each whorl also undergoes change, 

 and complicated alternations arise. Flowers the structure of which is otherwise 

 altogether different resemble one another in this respect, as is shown by the 

 Papaveraceae on the one hand (Fig. 464), and by the Cistineae and some Rosacese 

 on the other hand. 



Fig. 464.— Diagraiti of PapavefacecE ; A Ckelidintitan, a PapWver. 



The reduction of the flower to a simpler condition is often carried so far 

 in many Dicotyledons (as in Monocotyledons) that each individual flower consists 

 only either of an ovary with one or several stamens, or, when the arrangement 

 is diclinous, even only of a single ovary or of a single or several stamens; the 

 perianth being either entirely absent (as in Salix and Piperaceae) or reduced to a 

 cup-like structure {Populus, the female flower of Cannabineae, &c.) or to hair-like 

 scales among the sexual organs which represent the flower {e.g. Platanus). Flowers 

 of this kind are generally very small and densely crowded in large numbers in 

 the inflorescence (such as capitula, spikes, or catkins). In some cases it may even 

 be doubtful whether we have an inflorescence or a single flower, as in the genus 

 Euphorbia ^. 



The development of the separate parts and the entire form of the flower 

 in the mature state is so various that it is scarcely possible to state any general 



' Eichler, Ueber die Meilispermaceen, Denkschrift der k. bayer. Ges., Regensburg 1^4. — • 

 Payer, Organogenic de la fleur, PI. 45-49. — Eichler, Flora, 1865, Nos. 2-8 et seq. 



^ See Payer, I.e. p. 529; [also foot-note to p. 490. It is now generally admitted that the 

 Cyathiutn of Euphorbia is an inflorescence, a view which was first enunciated by Robert Brown in 

 opposition to Linnseus, who regarded it as a single flower. It appears that the stamens are here 

 axial (Warming, Ueb. poUenbildende Caulome und Phyllome, in Hanstein's Bet. Abhdl. 11, 1873)]. 



