THE PRINCIPLE OF NUMBER. 23 



usurJ, quincuucially arranged. The petals appear simul- 

 taneoushj, alternating in position to the sepals. The stamens 

 occur in ten rows, 5 being superposed to the petals and 

 5 to the sepals ; and, lastly, 5 carpels appear superposed 

 to the petals. This flower, then, adopts the more usual 

 character of alternation in the whorls. But it may be noticed 

 that while the corolla alternates with the calyx, each of 

 these outer whorls gives rise to a radial series of stamens. 



From the preceding illustrations, it will now be seen that 

 phyllotaxis lies at the foundation of the arrangements of the 

 members of floral whorls ; that the -| type prevails in the 

 sepals and petals, with a strict angular divergence of 144°. 

 The divergences are, however, subsequently modified in the 

 stamens and carpels. Thus, in Helleborus niger the petals 

 clearly represent a whorl of 21 parts, i.e. they are pre- 

 sumably arranged according to the -^^ type. They are, how- 

 ever, so far modified in position as to become superposed 

 to the sepals in groups. Similarly the stamens form 

 series of 21, each being superposed ia radial lines to the 

 petals. 



The interpretation of these displacements from what 

 would be due to strict, phyllotactical laws is that the 

 individual cords of the stamens and carpels are not inde- 

 pendent as they are in the " leaf traces " of an axial cylinder, 

 where the cord or cords belonging to each leaf are simply 

 intercalated side by side with those of the leaves most nearly 

 approaching the same vertical line, and constitute together 

 the common fibro-vascular cylinder of the stem. In the 

 pedicel, however, the rule is that this should contain at least 

 the same number of cords as there are leaves to the perianth, 

 or sepals and petals together. These, usually six or ten 

 cords, on reaching the floral receptacle are sent off respec- 

 tively as the cords of the sepals and petals ; whereas, it is 



