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.). 



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

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



fy 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 

 ias arranged cultivated corn into the following groups : 



Pod-corn, Zea tunicata. 

 Pop-corn, Zea cverta. 

 Flint-corn, Zea induraia. 

 Dent-corn, Zea indentata. 

 Soft corn, Zea amylacea. 

 Sweet corn, Zea saccharata. 

 Starchy sweet corn, Zea ainyleasaccliarata. 

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



'garded as varieties. Some of the forms under conditions of culture and 

 climate, revert to the original type. 



