So thats what the name means

Dryopteris erythrosora - translated from the botanical Latin means oak fern with red sori (the spore capsules on the frond undersides).  I'd never given the name much thought.  I grow it in open shade where it makes a nice upright, semi-evergreen, fronded fern with the distinct advantage that young foliage in late spring is a pleasing red bronze shade, very attractive in the garden setting.  But my plant has always been in a position where I look down on it so don't really notice the sori coming to maturity.  It took a chance gust of wind at exactly the right time to realise how apt the name was.

Red sori - just like it says on the label.