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A TEXTBOOK OF THEORETICAL BOTANY 



Fig. 1 149. — Melaleuca. Fascicles 

 of stamens with pedicels. 

 {After Van Tieghem.) 



a solid phalanx of stamens with all their filaments united and only the 



anthers free. 



The grouping of all the stamens into coherent bundles, or fascicles, 

 usually equal in number to the number of petals, is common in certain 

 families, such as Guttiferae, Loasaceae, Tiliaceae and Myrtaceae. Each 



fascicle originates as a single large primor- 

 dium, on which there arise a large number of 

 small protuberances which elongate into in- 

 dividual stamens, united by a common base. 

 This base normally remains short, but in 

 Melaleuca (Fig. 1149) and some other mem- 

 bers of the Myrtaceae it also elongates, so 

 that each fascicle appears to be mounted on 

 a long pedicel. The genus Candollea in the 

 Dilleniaceae presents a similar peculiarity. 

 There are five staminal filaments, in the 

 normal antisepalous position, but each fila- 

 ment bears at the top a cluster of five, elon- 

 gate, bilocular anthers, presumably represen- 

 ting a stamen fascicle with united filaments. 

 The facts of development, however, are not 

 known. The stamens of Citrus show a 

 partial and irregular fusion into groups of from two to six or seven stamens, 

 with their filaments united and their anthers free, but this is not fascicu- 

 lation in the strict sense, as all arise in a single whorl. It seems to be a case 

 of ordinary, though imperfect, synstemony. 



True branching of stamens is of rare occurrence and the only well- 

 known examples are in the genus Riciuus (Fig. 1150), and members of the 

 family Dilleniaceae. The apparent branching in the Tiliaceae is more 

 probably due to fasciculation. Indeed most cases of apparent branching are 

 due to this, or to partial fusions between stamens in the same whorl, as in 

 Citrus and Gunnera, or to a lateral expansion of the connective, separating 

 two halves of the anther, of which there are many examples {e.g., Salvia, 

 see Fig. 1141). In another direction it may sometimes be due to chorisis. 



The chorisis of stamens is a term which has been somewhat too widely 

 applied, including a number of cases where pairs of stamens stand together 

 in the flower at points where considerations of symmetry suggest that there 

 should be only one. The facts of ontogenetic development, where they are 

 known, may sometimes negative this conclusion, as in the cruciferous 

 flower. The two antero-posterior pairs of long stamens in this family 

 appear to interrupt the general dimery of the flower and have frequently 

 been cited as arising by the chorisis of two stamens. That this is not so is 

 shown by the existence of two separate stamen rudiments for each pair, 

 at least in most of the genera. True chorisis implies the division, at an 

 early stage, of a single rudiment into two, which develop completely in 

 independence. The pentamerous lateral flowers of Adoxa illustrate this. 



