An official website of the United States government
Here's how you know
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
As a library, NLM provides access to scientific literature. Inclusion in an NLM database does not imply endorsement of, or agreement with,
the contents by NLM or the National Institutes of Health.
Learn more:
PMC Disclaimer
|
PMC Copyright Notice
Part of this study was made while the writer was a member of the Department of Botany, Purdue Agricultural Experiment Station and of the Office of Cereal Crops and Diseases of the United States Department of Agriculture. It has been continued at the University of Michigan. Paper of the Department of Botany and of the University Herbarium, University of Michigan No. 397.