They call it photoperiodism
Contributors: Hambidge, Gove, 1890-
Series: Timely farm topics -- 38a; Farm science serves the nation -- 18; Timely farm topics -- 38a.
Publisher: U.S. Department of Agriculture
Published: 1945
Place of publication: [Washington, D.C.]
Language: eng
Subjects: Plant photoperiodism
Notes: Caption title.

Transcript of a radio broadcast.

"Recorded July 7, 1945."