400 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



ceous in texture. There is one exception to this condition — the kind 

 of corn called pod corn where each seed is enclosed in glumes which 

 in some strains are grotesquely enlarged (pi. 25, fig. 1). It was 

 thought at one time that this type of corn represented the ancestral 

 or primitive maize. When moderately developed, the glumes of pod 

 corn represent a less specialized condition, and hence a more primi- 

 tive form, than the membranaceous glumes of the ordinary types of 

 com. However, it does not follow that pod corn is the primitive maize. 

 It has been shown that this pecuhar type does not breed true and can 

 only survive as a hybrid with the normal form. Apparently the pure 

 form of pod corn is sterile — not a very satisfactory condition for an 

 ancestor. It is true that the podded condition is dominant to the usual 

 form, in hybrids between the two, and most wild types are dominant 

 to the derived forms. Also the cobs of pod corn easily become broken, 

 tending to separate the protected seeds, thus aiding somewhat in their 

 distribution. Despite the possession of these attributes of a wild plant, 

 pod corn seems no more able to persist unaided than the familiar 

 nonpod forms. Further, when it is crossed with a form of maize 

 having the primitive condition of branched ears, the combination, in- 

 stead of reconstituting a type of maize suitable for survival in the 

 wild, gives rise to a sterile monstrosity aptly called cauliflower (pi. 

 25, fig. 2). Pod corn therefore, though possessing a few primitive 

 features, must be classed with that host of misfits and abnormalities 

 of wliich there are scores in maize brought about by changes in the 

 ordinary heritable elements or genes. 



All of the relatives of maize have the seeds enclosed in glumes, and 

 in some the outer glume has been thickened to cover the seed, which 

 is deeply embedded in a cavity, or alveolus, in the rachis. Other 

 maize relatives such as Coix, have the seed completely enclosed in a 

 greatly modified leaf sheath, shell-like in texture. These modifica- 

 tions place the relatives of maize farther up the evolutionary tree than 

 maize itself and offer serious obstacles to the theory that corn has been 

 developed from its existing relatives by selection. 



Further, maize is much less stable than its relatives in the separa- 

 tion of the sexes — the basic characteristic of the tribe to which it 

 belongs. The development of female flowers in the tassel or of male 

 flowers on the ear of maize is a commonplace, and many true breeding 

 forms of this sort are known (pi. 26, fig. 1). In the relatives of maize 

 such aberrations are practically unknown, evolution in these relatives 

 of maize apparently having progressed to the point where the sexes 

 are completely separated. 



The characteristics that differentiate maize from its relatives are 

 all in the direction of fashioning a plant useful to man. The large 

 seeds, much larger than is required for the full nourishment of the 

 young seedling, the ear of kernels whereby all the seeds are securely 



