398 



Journal of Agricultural Research 



Vol. IV, No. s 



The mean ratio of the water requirement of each hybrid to the average 

 water requirement of its parents is o.99±o.oi. The probable error here 

 refers to the uncertainty of the individual ratios. In using the data as a 

 basis for predicting the probable departure of a hybrid from this ratio, the 

 observed departures must be considered — i. e., the probable error of a 

 single determination must be computed, which is found in this case to be 

 ±0.06. In other words, according to the data at hand, the chances are 

 that the water requirement of a hybrid will not depart from the mean 

 of its parents by more than 6 per cent. 



The relative amount of dry matter produced by hybrids and parents 

 is a point of interest in connection with the relative water requirement.* 

 In 1 91 2 and 191 3 the hybrids produced from 20 to 50 per cent more dry 

 matter than the mean production of the parent strains (Table III). In 

 1 914 three of the hybrids showed an increase in dry matter compared with 

 the parental mean, and one showed a decrease. An analysis of the indi- 

 vidual pot yields for both parents and hybrids shows that the pots giving 

 the greatest weight of dry matter usually have a water requirement below 

 the mean of the strain. The greater vegetative vigor of the maize hybrids 

 may therefore be correlated to some extent with the observed reduction 

 in the water requirement below the parental mean. 



Table III. — Dry matter produced by hybrid and parent strains of corn 



Year and parent strain. 



191: 



China 



Laguna. . . 



China 



Esperanza . 



1913- 



China . . . 

 Hopi .... 

 China. .. 

 Teosinte , 



1914. 



Algeria 4i7±2o 



Mean dry matter. 



Parent strain. 



Hybrid. 



Observed. Mean. l Observed. 



454 ±44 

 374±27 



454 ±44 

 536±i7 



S2i±i3 

 444±27 

 52i±i3 



547±2i 



China. 

 Budapest . 

 Joaquin . . 

 Budapest . 

 Pima. . . . 

 Joaquin. . 

 Pima. . . . 



387 ±12 



4ii±io 



283 ±17 



4ii±io 



36i±9 



283 ±17 



36i±9 



> 4i4±26 

 I 495 ±24 



} 483 ±15 

 I 534±i3 



> 402 ±12 

 I 347 ±10 

 } 386±7 



\ 322±IO 



6i4±32 



6l8±22 



723±5 

 641 ±17 



5i2±i5 

 399±ii 

 362 ±2 

 373±i3 



Ratio of 



hybrid to 



parental 



mean. 



I. 48±. 12 

 I. 25 ±.08 



I. 5o±. OS 



I. 20±. 04 



I. 27±. OS 



I- i5±-o5 



. 94±- 02 



I. i6±. 05 



' Collins has called attention to the marked increase in yield often noted 

 maize. (Collins, G. N. Tbevalue of first-generation hybrids in com. U.S. 

 Bui. 191, p. 33. 1910.) 



in first generation hybrids of 

 Dept. Agr. Bur. Plant IndiK. 



