ANGIOSPERMS. 431 



to divide the circle into equal parts ; if they are formed one after another succeeding 

 one another in the circle with a definite divergence, as is the case in most calyces of 

 three and five members, the fact may be indicated by placing the divergence after the 

 number of the members, as for instance in the formula for the Lineae S$%P$ 5/5 C$. 

 If on the other hand the members of a whorl arise one after another proceeding from 

 front to back, this may be shown by an upright arrow f , as in the formula for the 

 Papilionaceae 55 f PS T -St t 5 + 5 t Cl ; if they succeed one another from back to front, 

 the arrow may be reversed, as in the formula of Reseda Sn j Pn Stp \ + q \ Cr, where 

 letters are employed because of the variability of the numbers in the different whorls 1 * 

 The position also of the ovary may be indicated in the floral formula. A stroke over 

 the figure after the letter C, as C (3), means that the ovary is inferior, a stroke under the 

 figure, as C (3), that it is superior. When the calyx and corolla are not distinguished 

 from one another, they are called the perianth and designated by the letters Per, as in 

 the formula for the Liliaceae Per 3 + 3 St3 + 3 C (3), or that of the Amaryllideae with 

 an inferior ovary Per 3 + 3 St$ + 3 C (3). 



Order of development of the parts of the flower. The foliar structures are formed on 

 the axis of the floral shoot beneath the growing apex in the same acropetal order which 

 obtains on the axes of other shoots ; but in the formation of flowers it frequently 

 happens that the apical growth of the axis ceases or becomes very slow, while the tissue 

 of the axis (the torus) increases in circumference, and transverse zones of intercalary 

 growth are at the same time developed. In such circumstances the acropetal 

 succession is disturbed, and new floral whorls may be introduced between those already 

 formed ; and within the same whorl the separate members may appear in a very 

 different order, according as the leaf-forming zone of the torus developes uniformly all 

 round, as in polysymmetrical flowers, or the anterior or posterior side developes more 

 vigorously, as is the case especially in monosymmetrical (zygomorphous) flowers. 



These disturbances of the acropetal order of development are less marked in flowers 

 whose parts are spirally arranged 2 , the more numerous those parts are and the longer 

 the apical growth of the floral axis continues ; the spirally arranged parts are formed 

 one after another in ascending order and the divergence may be constant or may change. 

 Thus according to Payer in Ranunculaceae and Magnoliaceae the perianth-leaves and 

 the stamens arise in a continuous spiral, but each cycle is formed of a larger number of 

 stamens than of perianth-leaves ; in Helleborus odorus for example, in which all the 

 organs of the flower are spirally arranged, the corolline cycle contains thirteen, but each 

 staminal cycle twenty-one members. According to Braun the calyx in Delphinium 

 consolida is a cycle in which the parts have a f arrangement 3 ; then the divergence 

 changes but the deviation is small ; the first cycle after the change is formed by the 

 corolla, the three next by the stamens, and one carpel forms the termination. In the 

 section Garidella of Nigella the first cycle of the spiral with a divergence is formed 

 by the calyx, the second by the corolla, then comes a change to a f divergence, of 

 which the stamens occupy two cycles and above them are three or four carpels ; in the 

 section Delphinellum of Delphinium the calyx forms a cycle with a , the corolla one 

 with a f divergence, then follow two or three cycles of stamens with a divergence 

 approaching to f , and the spiral ends with three carpels. In the section Staphisagria 

 of Delphinium and in Aconitum the calyx forms one cycle of the spiral with the 

 divergence of f , the corolla another of f , the stamens are in one or two cycles with an 

 2 \ or a \\ divergence, and from three to five seldom more carpels end the spiral. In these 

 cases of relative position of parts it should be noticed that the members of the successive 

 cycles form orthostichies, if the divergence is constant, but the orthostichies pass into 

 oblique rows if the divergence undergoes a slight alteration. 



1 See next page. 



2 Payer, Organogenic, p. 707, and Braun, Ueber d. Bluthenbau d. Gattung Delphinium (Jahrb. 

 f. wiss. Bot.). 



3 See however the remarks below on sepals and petals with and i divergences (page 423). 



