Aug. i6, 1915 



Hybridization mid Water Requirement 



399 



The data presented indicate, so far as they are representative of first- 

 generation maize hybrids as a class, that striking differences between 

 the water requirement of hybrids and the mean water requirement of the 

 two parents are not to be expected. The greatest observed departure 

 of the hybrid from the parental mean was ±10 per cent, and, according 

 to the available measurements, the chances are even that first-generation 

 maize hybrids will not depart more than ± 6 per cent from the parental 

 mean. This departure, moreover, may take place in either direction — 

 i. e., the hybrid may resemble either parent as regards efiiciency in the 

 use of water. 



In investigations of this kind more extensive measurements are always 

 desired, both by the reader and the author. To determine with more 

 precision the correlation between hybrids and parents as regards water 

 requirement would necessitate a sufficiently large number of determina- 

 tions to justify the use of statistical methods. The expense and labor 

 involved in such measurements is great, each determination necessitating 

 the care of from 15 to 18 pots of plants throughout the growing season. 

 Since the results already obtained indicate that hybrids depart but 

 slightly from the mean water requirement of their parents, more extended 

 determinations are not believed to be justified at the present time. 



WHEAT HYBRID 



The wheat hybrid used was a cross between Triticutn durum and 

 Triticum aestivum. This hybrid strain has been grown for some genera- 

 tions and shows no increase in vegetative vigor as compared with the 

 parent strains. The dry matter produced was practically uniform for 

 parents and hybrid, but the grain yield of the hybrid was below its par- 

 ents, and this further increases the water requirement of the hybrid 

 when based on grain production. 



Reference to Table IV will show that the water requirement of the 

 hybrid is decidedly above both parents (14 ± i per cent above the paren- 

 tal mean). 



