The black stripes in this picture taken into the light are the spores of Hart's Tongue Fern (Asplenium scolopendrium). They grow as a brown, velvety, mass which contains thousands of them, on the backside of the fronds.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjUOz5gQfM9EOUcq1TY6xC3gB21N26npGcxstA5fa6DDOlwLi52EUbWYTng5h7WIEAMlS1PMCgniCSTO9SZeYRFeEt75sBP0Oa34I5dShZH9zmtZjSls9psKSaXu4Qlr2aWi9G71QtVvpwa/s280/asplenium+scolopendrium-118595%2526all-600-8s.jpg)
In spring young fronds emerge from between the old ones.