132. THE STRUCTURE OF ECONOMIC PLANTS 



flowers is very similar, "up to the time of differentiation of the 

 primordia of the stamen and pistil." As described by him, 



"The spikelet primordium makes its appearance as a rounded protuber- 

 ance on the rachis. The first differentiation to appear is the formation 

 of the lower glume, and it is soon followed by the upper one. (Fig. 55.) 

 The lemmae arise almost simultaneously with the appearance of the 

 stamens of the upper flower. From the lower side of the undiffer- 

 entiated end of the spikelet now appears the primordium of the lower 

 flower and the palea of the upper flower soon follows. The palea of 

 the lower flower appears much later. The older flower seems to be 

 terminal and the younger one lateral on the rachilla, but it is probably 

 better to consider both flowers lateral branches of this axis, which 

 terminates between the two paleae. ... In the development of 

 the flower from its primordium the stamens are first differentiated; 

 these are followed by the lodicules and the part that is left is the 

 primordium of the pistil. ... In both flowers of the male spikelet 

 the stamens and lodicules are fully developed but the development 

 of the pistils is soon arrested, and they disorganize." 



Fig. 55. Diagrams showing details of development of staminate spikelet: fl, flower pri- 

 mordium ; g, glume ; Im, lemma ; lo, lodicule; w, ovary wall ; p, palea ; psl, pistil ; st, sta- 

 men. (Redrawn after Weatherwax, Bull. Ton. Bot. Club.^ 



The Carpellate Inflorescence. — The carpellate inflorescence 

 is a thickened spike which ordinarily develops into the ear. Sev- 

 eral different views obtain as to the evolutionary development of 



