HIGHLY SPECIALIZED UNISEXUAL SPIKELETS 91 



staminate florets. The pistillate spikelets stand at 



right angles to their axis, the cob (Fig. 81, A). The 



glumes are minute, scarcely covering the ovary at 



flowering time (Fig. 81, B), and in the ripened grain 



remain as chaff on the cob, the greatly enlarged 



grain being naked. 



This grain, "a kernel ^ 



of corn," remains on 



the axis until loosened 



by force, 



Indian corn is 

 known only in culti- 

 vation. The problem 

 of its origin has not 

 yet been solved. We 

 only know that it 

 originated somewhere 

 in America, probably 

 on the uplands of 

 the tropics. It was 

 widely cultivated by the aborigines when the western 

 continents were discovered. The problem of the 

 morphology of the ear of com has not yet been satis- 

 factorily solved, but it is not at all difficult to recog- 

 nize the individual spikelets, both staminate and 

 pistillate. 



The student who has come this far will find it pos- 

 sible to dissect the inflorescence of any of our grasses, 

 with the possible exception of buffalo-grass, and to 

 distinguish the spikelets and the different organs. 



Fig. 81, A, part of cross-section of an 

 ear of corn, Zea Mays, showing two 

 pistillate spikelets standing at right 

 angles to their axis (the cob) ; B, pis- 

 tillate spikelet about flowering time; 

 C, part of raceme of staminate spike- 

 lets. 



