96 



to a single piece, the ungues form the tube, and the surfaces 

 the limb of the monopetalous corolla. Thus \ve have seen, 

 concludes von Martius, that the flower is that portion of the 

 ascending axis, in which the leaf, having undergone a four-fold 

 metamorphosis, ascends by degrees to its ultimate destination. 

 It is a four-times metamorphosed shortened branch, which has 

 departed from the nature of the leaf-bearing branch, &c. 



Third Lecture. On closer consideration of the formative 

 processes of the flower, several laws become apparent, such 

 as, 1st, the succession of four great stages of formation, the 

 whorl of calyx, corolla, stamens and pistil. In accordance 

 with the second law, the calyx and corolla consist each of one 

 whorl of leaves, on the contraiy, the series of the stamens 

 of two whorls. The third law is founded on the number in 

 the structure of the flower, as in regular flowers the num- 

 ber of the members of all whorls is the same. The num- 

 bers three and five appear most frequent in the whorls of the 

 flower : three prevails in Monocotyledons and five in Dico- 

 tyledons. Calyx and corolla generally remain constant to this 

 number, i. e. duplications occur rarely. When these whorls 

 consist of fewer members the case may be regarded as an ex- 

 ception. The series of the stamens is however more subject 

 to duplications. The numerical relation of the last whorl or 

 that of the pistil undergoes frequent reductions, especially in 

 Dicotyledons, where instead of five frequently only one or two 

 pistils occur ; at times it is also increased. The difference in 

 the numerical relation in the series and in the members of 

 the whorl of the fructification is exceedingly great in various 

 plants, sometimes the typical numbers remaining equal from 

 the calyx to the whorl of the pistil, or increasing towards the 

 centre of the flower, or decreasing in that direction. The 

 position of the members in the various whorls of fructifica- 

 tion depends on the consideration of the numerical law. It 

 is said, the members of the next succeeding whorl are so ar- 

 ranged that they alternate with one another, whence it re- 

 sults that the position of each leaf in the flower is a regular 

 one. The most general types of the flower, therefore, the 

 Monocotyledons and Dicotyledons, may be represented by 

 two diagrams, and M. von Martius then considers how this 

 formation may be compared to the process in operation at the 



