6o8 
PHANEROGAMS. 
of divergence, as in most trimerous or pentamerous calyces, this can be indicated by 
placing the angle of divergence after the number of the members ; thus the formula for 
Linaceae would be S^^j^P^St^C^. If, on the other hand, the members of a whorl are 
formed in succession from front to back, this may be shown by ^an arrow pointing 
upwards t, as in the formula for Papilionacese S^l Pgt St^] +5T Cj. If they are formed 
in succession from back to front, the arrow may be made to point downwards |, as 
in the formula for Reseda Sni Pnl Stpl + qi Cr, where the number of the parts is expressed 
by letters instead of figures in consequence of its variability \ 
4. Order of De'velopment of the Parts of the Floiver. The foliar structures arise on the 
axis of the floral shoot, as on other axes, in acropetal order below the growing apex. It 
is however not uncommon in the formation of flowers for the apical growth of the axis to 
cease altogether or to become extremely slow, while the receptacle continues to increase 
in breadth, and to develope transverse zones of intercalary growth. When this is the 
case the acropetal order of development is disturbed, and new whorls may become 
interposed between those already in existence. But even within the same floral whorl 
the individual members may be formed in a very different order of succession, according 
as the zone of the receptacle which bears the floral leaves is developed in a uniform 
manner all round (as in polysymmetrical flowers) or more rapidly on the anterior or 
the posterior side (which is especially the case in monosymmetrical or zygomorphic 
flowers). 
In flowers with a spiral arrangement of their parts'^, disturbances of the acropetal 
order of development are of less importance the more numerous the parts with a spiral 
arrangement, and the longer the apical growth of the floral axis continues. Those mem- 
bers which have a spiral arrangement arise one after the other in ascending order ; the 
angle of divergence may either be constant or may change. Thus, according to Payer, 
in Ranunculacese and Magnoliaceae the perianth-leaves and stamens arise in a con- 
tinuous spiral, but each turn of the spiral consists of a larger number of stamens 
than of perianth-leaves ; thus, e. g., in Helleborus odorus, where all the organs of the 
flower are arranged spirally, the corolline turn includes only thirteen petals, while 
each turn of stamens numbers twenty-one. According to Braun the turns of the 
calyx of Delphinium Consolida have a arrangement^; the divergence then under- 
goes a small change, but without materially deviating from ; the first turn with this 
altered arrangement is the corolla; the three following ones are the stamens, and the 
spiral terminates with a single carpel. In the section Garidella of Nigella the first of the 
turns with a ^5 angle of divergence is the calyx and the second the corolla; then follows 
a slight change in the angle to ^/g, the stamens forming one or two turns with this 
arrangement; and the spiral closes with three or four carpels. In the section Delphi- 
nellum of Delphinium the calyx constitutes a turn with ^sj the corolla one with "/g 
angle of divergence ; then follow two or three turns of stamens with the angle very 
near ^85 the spiral closing with three carpels. In the section Staphisagria of the same 
genus, and in Aconitum, the calyx forms a turn with the corolla one with angle ; 
the stamens stand in one or two turns with the divergence 721 or ^734? concluding 
with three, five, or rarely a larger number of carpels. It must be noted in reference to 
these arrangements that the members of successive turns stand in orthostichies when 
the angle of divergence remains constant ; but that the orthostichies pass into oblique 
rows when the divergence undergoes a small change. 
The first thing to observe in cyclic flowers (/. e. those in which the parts are arranged 
in whorls) is the order of formation of the whorls with respect to one another, and then 
^ See Payer, Organogenic de la fleur ; also the next paragraph. 
^ Compare Payer, Organogenic de la fleur, pp. 707 et seq.; and Braun, Jahrb. für wissensch. Bot. I, 
Ueber den Blüthenbau der Gattung Delphitiium. 
3 Compare with this what is said below respecting sepals and petals which are formed with the 
angle of divergence Y3 and Y^. 
