176 THE FLOWER. 



321. Numerical ground-plan. Many flowers are numerically 

 indefinite in some or most of their kinds of members, as Ranun- 

 culus, Magnolia, and the Rose for stamens and pistils, N}-m- 

 phsea for all but perhaps the sepals, many Cactaceae for all but 

 the pistil, and Calycanthus for all four components. But more 

 commonly each flower is constructed upon a definite numerical 

 ground-plan ; and the number is usually low. Seldom, if ever, 

 is it reduced to unity in a hermaphrodite blossom (even II ip- 

 puris, with a single stamen and a single pistil, is not an un- 

 equivocal case) , and probably never in a complete one. But there 

 are such extremely simplified flowers among those of a single sex. 

 In Monocot}'ledons, the almost universal number is three, some- 

 times two ; in ordinary Dicotyledons, five prevails ; four and two 

 are not uncommon ; three is occasional ; and higher numbers are 

 not wanting, as twelve or more in Houseleeks. 



322. To designate the particular plan, such familiar terms of 

 Latin derivation as binary, ternary, quaternary, quinary, senary, 

 &c., are sometimes employed, denoting that the parts of the 

 flower are in twos, threes, fours, fives, or sixes. More technical 

 and precise terms, equivalent to these, are composed of the Greek 

 numerals prefixed to the word meaning parts or members, as 



Monomerous, for the case of a flower of one member of each ; 



Dimerous, of two, or on the plan of two members of each ; 



Trimerous, of three, or on the plan of three members ; 



Tetramerous, of four, or on the quaternary plan ; ^ 



Pentamerous, of five, or on the quinary plan ; 



Hexameroiis, 1 of six, or on the plan of six members to each 

 circle. But, in Monocotyledons, so-called hexamerous blossoms 

 are really trimerous, the sixes being double sets of three. 



323. Pattern Flowers. These should be symmetrical, regular, 



complete in all the parts and without ex- 

 cess or complication of these, and with- 

 out any of the cohesions or adhesions 

 which may obscure the type, or render it 

 bss expressive of the idea that a flower 

 onsists of a series of circles or spirals 

 of modified leaves crowded on a short 

 axis. Wherefore the illustration Fig. 307, 

 with its diagram Fig. 308, ma}' serve as a pattern pentamerous 

 or quinaiy flower; and Fig. 326, with its diagram, Fig. 327, 



1 These may be shortly written 1-merous, 2-merous, 3-merous, and so on up 

 to 10-merous (decamerous), 12-merous (dodecamerous), c. 



Fig. 326. Parts of a symmetrical trimerous flower (Tillaea muscosa): a. calyx; 

 b corolla; c. stamens; d. pistils. 327. Diagram of the same. 



