SPERMATOPHYTA—GRAMINEAE— GRASSES 341 



Fig. 139. Vanilla grass {Hierochloe odor- 

 ata). a. Spikelet with nearly equal lower glumes; 

 b, with lower glumes removed, showing third and 

 fourth scabrous glumes; c, palea with stamens; 

 d, pistil. (Div. of Agros. U. S. Dept. of Agric). 



the terminal, staminate inflorescence forms the "spindle" and the long, pro- 

 jecting styles of the pistillate flowers constitute the "silk"; the cob is formed 

 by the union of the axes of several female spikes into a much thickened body. 

 The 1 or 2 species are of American origin, presenting many varieties in 

 cultivation known as corn, Indian corn or maize {Zea Mays). Dr. Sturtevant 

 has arranged cultivated corn into the following groups : 



Pod-corn, Zea tunicata. 



Pop-corn, Zea everta. 



Flint-corn, Zea indurata. 



Dent-corn, Zea indcntata. 



Soft corn, Zea aynylacea. 



Sweet corn, Zea saccharata. 



Starchy sweet corn, Zea ainyleasaccharata. 

 The so-called species and groups of Dr. Sturtevant are hardly to be re- 

 garded as va-rieties. Some of the forms under conditions of culture and 

 climate, revert to the original type. 



