FLORAL hlAGRAMS. 129 



106. In cyclic flowers, whilst there is usually one 

 whorl each of sepals, petals, and carpels, there are not 

 unfrequently two whorls of stamens. If each whorl is 

 made up of the same number of members the flower is 

 isomerous, and will, at the same time, be monomerous, 

 dimerous, irimerous, tetramerous, or pentamerous, accord- 

 ing as each whorl contains one, two, three, four, or five - 

 members. If the numbers of the members in the whorls 

 do not correspond, the flowers are heteromerous. 



197. The relations of the whorls to each other in ahy 

 particular case may be very conveniently exhibited by a 

 diagram. Fig. 173, for example, 

 shows the plan of a Lily. The dot at 

 the top of the figure represents the 

 position of the axis of the plant, and 

 should always be shown in a floral 

 diagram. The side of the flower 

 Fig. 173. towards the stem is the posterior side, 



the opposite one being anterior, and a plane passing 

 through the centre of the flower and also through the 

 stem or axis is called the median plane. We have in the' 

 flower of the Lily an outer whorl of three members ; then 

 alternately with these (and this is the usual plan in 

 cyclic flowers) a second whorl of three members ; then 

 the outer whorl of stamens, also three in number; then 

 the three inner stamens ; and, finally, the three carpels. 



198. The composition of this flower may also be 



expressed by a formula, as follows : Kg, O3, A3+3, G( ), 



where K stands for calyx, C for corolla, A for anthers, 



G for gyncecium. The brackets enclosing the figure 



Fig. 173.— Diagram of Lily flower. (PrantL) 



