n. pl. so·ri (sôrī)
1. A cluster of sporangia borne on the underside of a fern frond. Also called fruit dot.
2. A reproductive structure in certain fungi and lichens.
[New Latin sōrus, from Greek sōros, heap; see teuə- in the Appendix of Indo-European roots.]
(click for a larger image)sorus
sori on the frond of
a polypody fern
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.