52 HAKSHBKkCiKK ; 



branches bearing lateral axes, with pistillate spikelets of two 

 flowers each below, and stamiuate two-flowered spikelets 

 above. Through extensive cultivation, the lower branches 

 being more generously nourished, developed ultimately only 

 pistillate flowers, the male flowers being crowded out, or sup- 

 pressed, by the two-ranked, pistillate spikelets. The terminal 

 part of the plant, originally an androgynous spike, because of 

 its position, tended toward the suppression of the pistillate 

 spikelets until the terminal axis came to bear only staminate 

 flowers. These are produced in pairs in each separate male 

 spikelet, as in the original condition, while in the cultivated 

 corn, by a crowding of the spikelets together, one of the pis- 

 tillate flowers has become rudimentary. The structure of 

 this abnormal specimen suggests this, and the view is 

 strengthened if we cotnpare it with ordinar)' corn, with teo- 

 sinte, and with the closely related gam a grass ( Tripsacuvi 

 dactyloidis ), where the pistillate flowers and the staminate 

 flowers are borne on the same axis of inflorescence and in a 

 two-ranked fashion. All of this is pure speculation, but we 

 have now reached the place in our methods of breeding, 

 where I think the test of all our theories can be made. If 

 we study the phenomena of reversion, we find that in most 

 cases such reversion occurs when two varieties which are 

 crossed each contain certain factors lacking in the other, of 

 which the full com]ile!nent is necessary for the production of 

 the reversionary wild form. This at once suggests the idea 

 that the various domestic forms of animals and plants have 

 arisen by the omission from time to time of this factor, or of 

 that. Nevertheless there are other cases where we must 

 suppose evolution to have proceeded by the addition of char- 

 acters. So that domestic varieties may arise by a process of 

 atldition of factors in some cases, and of subtraction in 

 others. In the domestication of corn, it has been the sup- 

 pression of male flowers on the lower branches and the multi- 

 l)lication oi ])istillate ones, while on the terminal axis the 

 pistillate flowers have been subtracted and the staminate ones 



