Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Ascyrum' from the website Trees and Shrubs Online (treesandshrubsonline.
A small genus of N. American plants closely allied to Hypericum, but well distinguished by having four sepals and petals instead of five.
Ascyrum is no longer recognised as a genus distinct from Hypericum, the tetramerous corolla characterising this group being of too trivial a nature to justify generic or even sectional rank. The species described – A. hypericoides L. – becomes H. hypericoides (L.) Crantz.