234 



THE FLOWER. 



439. Having already noticed the symmetrical arrangement of the 

 foliage (236-251), and remarked the transition of ordinary leaves 

 rf into those of the blossom 



(42G),we naturally seek 

 to bring the two under 

 the same general laws, 

 and look upon each floral 

 whorl as answering ei- 

 ther to a cycle of alter- 

 nate leaves with their m 

 respective intemodes undeveloped, 

 or to a pair or verticil of opposite 

 or verticillate leaves. Thus, the simplest com- 

 bination, where the organs are dimerous, or in 

 two 3, may be compared with the alternate two- 

 ranked arrangement (238), the calyx, the corolla, 

 stamens, &c. each consisting of one cycle of two 

 elements ; or else with the case of opposite leaves 

 (250), when each set would answer to a pair of 

 leaves. So, likewise, the organs of a trimerous 

 flower (viz. one with its parts in threes, as in Fig. 

 353) may be taken either as cycles of alternate 

 334 leaves of the tristichous mode (239), with the axis 

 shortened, which would throw the parts into successive whorls of 

 threes, or else as proper verticils of three leaves ; while those of a 

 pentamerous or quinary flower (with the parts in fives, as in Fig. 354) 

 would answer to the cycles of the \ arrangement (240) of alternate 

 leaves, or to proper five-leaved verticils. So the whorls of a tetra- 

 merous flower are to be compared with the case of decussating op- 



thc Greek numerals combined with jue'po?, a part. Thus a flower with only one 

 organ of each kind, as in the diagram, Fig. 352, is monomerous : a flower or a 

 whorl of two organs is dimerous (Fig 373) ; of three (as in Fig 353), trimeious; 

 of four, Mramerous (Fig. 405) ; of five (as in Fig. 334), pentamerous; of six, hex- 

 amerous ; of ten, decamerous, &c. These words are often printed with figures, as 

 2-merous, 3-merOus, i-merous, 5-merous, and so on. 



FIG. 353. Parts of a symmetrical trimerous flower (Tilloea museosa) : a, calyx ; 6, corolla ; 

 e, stamens ; d. pistils 



F!G. 334 Ideal plan of a plant, with the simple stem terminated by a symmetrical penta- 

 merous flower ; the different sets of organs separated to some distance from each other, to show 

 the relative situation of the parts j one of each, namely, a, a sepal, b, a petal, c, a stamen, and 

 d, a pistil, also shown, enl irged. 



