Fig. 135. Equigetum arvense, a common horsetail: 1, three fertile shoots rising from 

 the dorsiventral stem, showing the cycles of coalesced scale-leaves at the joints 

 and the terminal strobili with numerous sporophylls, that at a being mature; 2, 

 a sterile shoot from the same stem, showing branching; 3, a single peltate sporo- 

 phyll bearing sporangia; 4, view of sporophyll from beneath, showing dehiscence 

 of sporangia; 5, 6, 7, spores, showing the unwinding of the outer coat, which aids 

 in dispersal.— After Wossidlo. 



