then becomes comparable to the varieties of inbred peas and beans, 
in that its continued self-fertilization will give seed which will 
produce only plants similar to itself and of equal vigor. But 
increased vigor and productiveness always occur, just as in the 
case of the pea, when two of these inbred maize strains are 
crossed. Inbreeding may be said to result in isolating man}’ 
pure strains or types, some vigorous, some weak, but none of 
which are degenerates directly caused by this method of repro- 
duction. 
The increased productiveness is strikingly shown in the pho- 
tograph of Learning maize ( Fig. 4) , loaned by the Connecticut Agri- 
cultural Experiment Station. On each side are the parents, the 
center being occupied by a typical sample ear of the first ( F j ) 
generation progeny. A still better idea of the increased produc- 
tiveness of first generation hybrid corn over the parent strains 
may be gained from Bulletin No. 243, Bureau of Plant Industry 
(plates iv and v, pp. 19-26). In the work on which this bulletin 
was based, two strains of maize were isolated by inbreeding, one 
of which produced in a given year 47.7 bushels per acre, the 
other yielding only 16.6 bushels. The crossed seed from these 
two parents produced 117.5 bushels per acre. Of course, this 
difference in productiveness between the parent generations and 
their first filial hybrid generation is not always so marked, but 
generally the increase is great enough to make the method very 
important commercially. In practice, the parent varieties are 
planted in alternate rows and the tassels are completely removed 
from one variety. The ears of hybrid corn occur only on the 
detasseled rows, and these, when planted, give the large yields. 
In order to insure the continuance of this great productiveness, 
new crossed seed must be obtained in this mannereach year, as 
the second (F s ) generation does not yield so well. As theeorn crop 
in the United States in 1909 was valued at $1 ,720,CC0,000, heading 
the list or agricultural crops in money value, one can readily see 
the great commercial importance of such a method of increasing 
yield. 
Most corn is either proterandrous or synacmic. In the first 
case, the tassels mature before the silks; while in the second, the 
tassels and silks mature simultaneously. A field of proteran- 
