REPRODUCTION 



193 



units of the pistil arc inoiphologically leaves; and that the earliest 

 floral type was perfectly regular, with its various parts rather 

 numerous and with no fusion whatever between circles or between 

 inenil)ers of the same circle. 



Inflorescence.— T\ie arrangement of flowers on the plant is 

 known as the inflorescence. The flowers may be solitary, arising 

 from the ground, or singly in the axils of the leaves (Figs. 233 



Fig. 107.— Wind-pollinated flowers of the alder {Alnus). The long catkins 

 are groups of male flowers just ready to shed their pollen. The smallest catkins 

 are composed of female flowers, their stigmas ready to receive the pollen blown 

 through the air. The woody cones of last year, which developed from the female 

 catkins and have shed their seed, are also shown. 



and 240); or the leaves may be reduced to small bracts, the inter- 

 nodes shortened, and the flowers thus grouped into definite 

 clusters. Such clusters are of various types as to shape and 

 arrangement, the commonest among them being the raceme 

 (Fig. 234), spike, head (Fig. 236), umbel (Fig. 235), corymb, 

 panicle, and cyme. 



Pollination.— The first step in the accomplishment of repro- 

 duction is the transfer of pollen from the anthers to the stigma, 

 a process known as pollination. At about the time the flower 

 unfolds, the anthers open and hberate the pollen grains. In 

 rare cases the stigma lies so close to the anthers that the pollen is 



