loi THE STRUCTURE OF ECONOMIC PLANTS 



The Floral Axis. — The flowers are borne in simple umbels 

 at the apex of a floral stem which is commonly hollow when 

 mature, and somewhat swollen at its middle or near the base. 

 (Fig. 94.) The number of floral stems per plant may vary from 





Vrs. . 



Fig. 94. Field of Yellow Globe onions. (Qjurtesy of Ferry-Morse Seed Co.) 



one to twenty or more, depending upon the variety and the size 

 of the mother bulb. In the development of the floral axis, the first 

 structure to arise is the bract which encloses it. The primordium 

 of this bract originates at a point opposite the youngest leaf blade, 

 and it is not until the central axis begins to elongate to form the 

 flower stalk that it can be determined whether the leaf-like struc- 

 ture is a bract or another vegetative leaf. The bract encloses the 



