Plural of archesporium; multiple instances or variations of spore-forming tissue in plants.
From 'archesporium' plus Latin plural suffix '-a.' This is the standard Latin plural used in botanical and scientific texts when discussing multiple spore-forming tissues.
This looks like a typo with the extra 's,' but it shows how even scientific terminology can have spelling variations—scientists were still standardizing Latin plurals well into the 20th century!
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