ANGIOSPERMS. 



527 



consisting of five alternating whorls, each with three members, of which the two outer 

 ones constitute the perianth, the two next the androecium, and the last the gynsceum • 

 although the latter may sometimes be represented by two whorls. Occasionally instead 

 of abortion an increase of number takes place in particular whorls, by the formation 

 of one member instead of two (as in Butomus, Fig. 351, p. 489). 



Increase in the typical number of the members of a whorl may arise in different 

 ways, as the following examples will show. According to the detailed researches of 

 Eichler^, the flowers of Fumariaceai may be referred to a type in which there are six 

 decussate pairs of members (Fig. 380), viz. — 



two median sepals, 



two lower lateral (exterior) petals, 



two upper median (interior) petals, 



two lateral stamens, 



two median (always abortive) stamens, 



two lateral carpels. 



Ihe two lateral stamens are however represented in some genera (as Dicentra and 

 C:orydaIis) by two groups, each consisting of three stamens, an inner one with an entire 

 quadrilocular anther, and two lateral stamens each with a bilocular anther, a struc- 



ric. 381 — Dia^rraiu of the llower of Capparidea; ; ./ Cleoiite dro- 

 serajol.a, S Po.'txuisia araveoUns (after Eichler). 



Fig. 3«i2 



-Diagram of the flower of 

 Cruciferce. 



ture which Kichlcr explains on the hypothesis that the lateral stamens are only stipular 

 structures, and therefore branches from the base of the middle one. In Hypecoum 

 Eichler assumes a cohesion of each pair of opposite stipular stamens so as to form an 

 apparent whorl of four stamens. 



Eichler also deduces the flowers of Gruciferae and Cleomeae (a section of Cappa- 

 rideae) from a type represented by Fig. 381 A, which is also the empirical diagram for 

 Cleome droserafolia, and for certain species of Lepidium, Senebiera, and Capsella. This 

 typical flower consists of 



two lower median sepals, 



two upper lateral sepals, 



four diagonal petals in one whorl, 



two lower lateral stamens, 



two upper median stamens, 



two lateral carpels. 



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 Crucifers usually two (Fig. 382), in the 

 Gleomeae sometimes two, sometimes more (Fig. 381 B). Such a replacement of one 



» Eichler, Ueber den Bliithenbau der Fumariaceen, Crucifeien, und einiger Capparideen, in 

 (Regensburg) Flora 1865, nos. 28-35, and 1869, p. i.— Peyritsch, Ueber Bildungsabweichungen der 

 Ciuciferenbliithen, Jahrb. fOr wiss. Bot. vol. VITI, p. 117. 



