98 



ESSENTIALS OF VEGETABLE PHARMACOGNOSY 



form, (Fig. 373A). If but one brancli 

 gro^' from a node, and these snccessively 

 from right to left, the zig-zag or Flexuose 

 form of rhachis is produced (Fig. 3730), 

 and if constantly from the same side, or 

 apparently so, the Cireinate (Fig. 373B). 

 The descending or hasipetal nature of 

 the definite inflorescence is clearly 

 shown when the successive branches re- 

 main short, each successively developed 

 flower remaining at a lower level than 

 that which preceded it. Instead, how- 

 ever, of assuming either of these two 

 states, in which the flowers remain at 

 different levels, the branches may radiate 

 and elongate to different degrees, ceasing 

 their elongation when their flowers have 

 been brought to a uniform height, so that 

 a more or less flat-topped inflorescence 



results, the order of development being 

 form the centre outward, or Centrifugal, 



as in the branches of Fig. 49-4. This 

 form represents the true Cyme, and be- 

 cause of their relationship to it this en- 

 tire series of inflorescence is often de- 

 nominated the Cymose. It will thus be 

 seen that in different forms of the cymose 

 inflorescence^ we may have the flowers 

 (a) all brought at length to a uniform 

 level (b), those successively later devel- 

 oped brought to successively higher 

 points, and (c) those left at successively 

 lower levels- This fact demonstrates 

 that the cymose or descending nature of 

 an inflorescence cannot be determined by 

 noting the relative heights of the flowers 

 themselves, but only by noting the order 

 of their development. 



Itt the other series the first flower to 

 develop is structurally the lowest of the 

 cluster, the succession being upward, 

 Ascending or Acropetal (Figs. 4S9 and 

 490). If the successive branches develop 

 less rapidly than their predecessors the 

 result is again a flat topped inflorescence 

 with the development from; the outside 

 to centre, or Centripetal (Figs. 487 and 

 488), The branches and flowers may be 

 separated on obvious peduncles and pedi- 

 cels, or these may be not apparent, the 

 flowers being sessile. In accordance 

 with the characters above explained, we 



obtain the following simple forms of 



thotaxy ; — 



Series 1. 



Ascending, Acropetal, Indefinite, Inde- 

 terminate, Centripetal or Botryose 

 Forms. 



A. With the rhachis not elongated. 

 1. The Capitulum or Head, with 

 the flowers, and branches if 

 any, sessile or so regarded 

 (Fig. 486). 



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2. The Corymb, with the rhachis 

 manifest, though short, and its 

 pedicels or branches elongated 

 so as to produce a flat-topped in- 

 florescence (Fig, 487). 



3. The Umbel, similar to the 

 Corymb but with the rhachis 

 not manifest, so that the pedi- 

 cels or branches all appear to 



