ARRANGEMENT OF THE PARTS OF THE FLOWER. 469 



s 



K 



P5 



5 



St 5. 



Owing to the abortion of the petals in Amaranthaceae, Cheno- 

 podiaceae, Drticacese, Santalaceae, &c, an appearance of superpo- 

 sition of the stamens is brought about, though in truth this is in 

 these cases their natural position. 



In 



Maout 



Decaisne, Gen. Syst. ed. Hook. p. 303, is 



S5 

 St 5 

 5, 



- 



owing probably to the abortion or suppression of a row of petals. 

 Abortion or suppression of an outer row of stamens will probably 

 account for the position of the stamens in the Apostasiaceae and 



Burmanniaceae. 



5. Bleiomery. — When the members of successive whorls are not 

 equal in number, but anisomerous, some of the additional parts 

 must necessarily be superposed to others in the preceding whorls ; 

 thus in Nigella, where within a calyx of five sepals is a row of 

 ten petals, some of those petals must be more or less superposed 

 to the sepals. In Casearia, where there are no petals, but a calyx 

 of five sepals, the staminal whorl may be thus represented 



S5 



St 10 x 10. 



The formula for Byrsanthus epigynus* is 



S5 



P5 



x St x St 

 x St. 



In such cases it becomes necessary to inquire to what cause the 

 polymery is due. It may arise from branching of the stamen 

 chorisis, or from interposition of parts. Cases of this kind occur 

 in ErytJiroxylon, Oxalis, Malpighia, Zygophyllum, Quassia, Melia, 

 many Sapindaceae, Saxifragaceae, Crassulaceae, ¥r&ncoa,ce&,I>ion<ea, 

 some Combretaceae, Melastomaceae, Ericaceae, Kypopitys, Bougain- 

 villea, Tetragonia, Phytolacca, Alisma, Butomus, etc. 



* Mast, in Joum. of Linn. Soc. vol. xiii. p. 15. 



