1 174 A TEXTBOOK OF THEORETICAL BOTANY 



often decorated with a sort of paracorolla round the top, surrounding tne 

 anthers (Fig. 1145). 



When all the stamens are united they are said to be monadelphous ; 

 when in two groups, diadelphous and so on. 



Fig. 1 145. — Azadiracliiu indica. Meliaceae. 

 A, Flower cut lengthways, showing the 

 well-developed staminal tube. Perianth 

 removed. B, Part of top of tube en- 

 larged. C. Top of the tube showing the 

 petaloid appendages to the anthers. 

 {After Engler-Prantl.) 



Fig. 1 1 46. — Coiiroupilu sminamensis. An- 

 droecium showing the phalanx of united 

 stamens which is inverted over the 

 centre of the flower. {After he Maoiit 

 and Decdisne.) 



Coiiroiipita, the Cannon Ball Tree (Myrtaceae) (Fig. 1146), has a mona- 

 delphous arrangement of stamens which is unique. They are very 

 numerous and are all united by their filaments into the shape of a bowl 

 around the gynoecium. On one side of the bowl the filaments are short and 

 upright, but on the other side they are prolonged into a broad band, which 

 curves up over the stigma, covering it and the whole top of the flower with a 

 mass of downwardly pointing anthers. The Papilionaceae present varying 

 conditions, which are of systematic significance, certain genera being 

 monadelphous and others diadelphous, a single stamen, usually the pos- 

 terior one, remaining free while the others are concrescent. The dia- 

 delphous condition is well illustrated in the Fumariaceae, where the 

 stamens are grouped into two compound structures, or phalanges, each 

 consisting of one middle stamen with two half-stamens attached to its 

 sides, the filaments forming a broad band and the anthers being free 

 (Fig. 1 147). 



Most of the above examples of concrescence are congenital, that is they 

 arise by union of the organ primordia. This reaches its limit in cases where 

 the separate identity of the primordia is lost and the united structures 

 arise from a common, usually ring-like, basis. A later union, or growing 



