ANGIOSPERMS. 



605 



Deviations from this type are produced by the formation of two or more stamens in 

 place of each of the upper (inner) ones; in the Gruciferae usually two (Fig. 413), in the 

 Gleomeae sometimes two, sometimes more (Fig. 412 B). Such a replacement of one 

 stamen by two or more is termed by Payer Dedoublement'^, by Eichler and others Colla- 

 teral Chorisis, and must apparently be considered as a branching of very early origin. 

 This view is confirmed in this case by the fact that in the Crucifer Atelanthera the 



Fig. 412— Diagram of the flower of Capparideae ; A Cleome di-o- 

 serafolia, B Polanisia graveoUits (after Eichler). 



Fig. 413.— Diagram of the flower of 

 Gruciferae. 



median stamens are only split and the two halves of each provided with half-anthers, 

 while in Crambe each of the four inner stamens puts out a lateral sterile branch, which 

 may be explained as the commencement of a further multiplication of the stamens 

 such as actually occurs in the Crucifer Megacarpeea and in many Gleomeae. Even if 

 the way in which increase of the typical dimerous number of the inner whorl of stamens 

 has been brought about be still obscure, it appears certain that the inconstancy of 

 the number of the members of the staminal whorl proves that in Gruciferae and Gle- 

 omeae a deviation has arisen in this part of the flower from the typical dimerous number, 

 while the other whorls have remained unchanged. The only 'deviation which occurs in 

 the gynaeceum of the Grucifers is in the genera Tetrapoma and Holargidiunty where, 

 besides the two lateral carpels, two median ones are also .produced, thus forming a 

 four-lobed ovary '^. 



An essentially different kind of increase in the typical number of the members of a 

 floral whorl may be caused by the formation in the still very young bud of new 

 members of the same kind between those already in existence and on the same zone 



Fig. 414.— Diagram of the flower oi Dictamnus Fraxinella {ff. Fig. 38 ). 



of the receptacle ; /. e. by what we have already described as the Interposition of new 

 members. This I found to occur, for example, in Dictamnus Fraxinella (Fig. 388), and 

 is represented in the diagram. Fig. 414, by the stamens of later origin being shaded not so 

 dark as those of earlier origin. It may, I think, be inferred from Payer's descriptions 



^ [The theory of an original dimerous symmetry in the flowers of Gruciferae has been pushed 

 still further by Meschaeff (Bull. Soc. Imp. Nat. Mosc), who regards the four petals as also the result 

 of a lateral dedoublement of a single pair (see Bentham, Ann. Address Linn. Soc. 1873).] 



2 [Holargidium is a section of Draba. According to Bentham and Hooker the four carpels of 

 Tetrapoma are an abnormality not constant under cultivation. The same authors also mention the 

 occasional occurrence of a similar abnormality in Brassica and Nasturtium.'] 



