The Origin of Wheat. 163 



will die out at once), what sort of result shall we 



finally get ? 



In the first place, the calyx, consisting of three 



pieces, will stand towards the crowded stem or axis in 



such a fashion that one piece will be free and exterior, 



while two pieces will be interior and next the stem, 



thus — 



O 



a a 



Now, the effect of constant crushing in this direction 

 will be that the two inner calyx-pieces will be slowly 

 dwarfed, and will tend to coalesce with one another ; 

 and this is what has actually happened with the inner 

 pale of wheat and of other grasses, though the mid- 

 ribs of the two originally separate pieces still show 

 on the compound pale, like dark green lines down its 

 centre. Thus, in the fully developed grasses, in place 

 of a trinary calyx, we get two chaffy scales or pales, 

 the outer one representing a single sepal, and the 

 inner one, which iias been dwarfed by pressure 

 against the stem, representing two sepals rolled into 

 one, with two midribs still remaining as evidence of 

 their original distinctness. 



Next, in the case of the petals, which alternate 

 with the sepals of the calyx, the relation to the stem 

 is exactly reversed ; for we have here two petals free 



