xiv INTRODUCTION 



The orchids have the compound ovary of the lilies, and the raised corolla oi 

 the irises, but have gone a step farther by developing a very irregular 

 corolla, one petal usually taking the form of a lip or sack. 



In advancing from the buttercups to the mints, the first change noticed 

 is the union of the simple pistils into a compound one. The poppies still 

 show a close connection with the buttercups in the numerous stamens, 

 while in the other families of the mustard and higher orders, reduction 

 in number is apparent. The number of sepals and petals becomes regularly 

 5, with 4 frequent, while 6, 7, 8 and 9 are very rare. The number of 

 stamens and of cells of the ovary varies somewhat more widely but is often 

 constant for the different groups. Thus the mallows are characterized by 

 many stamens grown together in a tube at the base ; the geraniums, flaxes and 

 oxalises have always a 5-celled ovary, while the pinks have a 1-celled ovary, 

 which is made up of a varying number of carpels as shown by the styles. 

 All these groups between the buttercups and primroses possess but the one 

 step of advance over the buttercups, i. e., the union of several simple pistils 

 into a compound one. The characteristics which separate the different 

 families from one another in this region are minor ones of differences of 

 number in stamens or cells of the ovary, or other differences, not apparent 

 in a flower-formula. The primrose group is marked off from the preceding 

 by the added union of the petals with each other into a bell-shaped or tube- 

 shaped corolla. From the pinks onward in this line of development, all 

 flowers must possess the two steps of advance, i. e. united pistils, or a com- 

 pound ovary, and united petals. The two most highly developed groups, 

 the snapdragons and mints, have added to these the third step of irregu- 

 larity of corolla, and this organ is characteristically a 2-lipped or variously 

 irregular tube. Thus the buttercup-mint line terminates its development, 

 as the buttercup-orchid line has, in a highly specialized form of corolla, but 

 differs from it in having united the petals instead of elevating them upon 

 the ovary. The two have arrived at much the same stage of development 

 but by different methods. 



Turning to the buttercup-aster line, it will be seen that all the methods 

 possible have been made use of in this line of development. The right- 

 hand and left-hand lines have taken the same initial step, that of uniting 

 the simple pistils unto a common ovary. The middle line shows elevation 

 of the petals upon the calyx or ovary as the first step, though the second 

 step of uniting the simple pistils follows very quickly. The rose order ex- 

 hibits among its many families all variations from separate pistils on the 

 same level and separate pistils below the corolla, to compound pistils at 

 the normal level and compound pistils below the corolla. The orders 

 and families just above the roses however, are characterized by the com- 



