12 Nebraska Experiment Station Research Bui. 15 
well-defined place of their own. In some cases they are 
treated as annuals and in other cases as perennials. This 
being the case, one is justified in saying that, in general, 
there are but two large divisions of field crops, one division 
treated as annuals and the other as perennials. 
Crops treated as annuals divide into three groups com- 
monly spoken of as fall or winter annuals, spring annuals, 
and summer annuals. Winter annuals are usually seeded in 
the fall, live thru the winter, bear fruit and die the following 
summer. Spring annuals are seeded either in the late winter 
or during the spring and are harvested in the summer or 
early fall. Summer annuals are planted either in the late 
spring or early summer and are harvested during the fall and 
early winter. 
This part of the bulletin deals principally with the acre- 
age of the various field crops listed in the census that are 
treated as cultivated annuals. It appears that the variation in 
the acreage of the three groups of crops belonging to this 
division affords one of the best possible measures of the effect 
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