THE FERNS 



541 



Fig. 369. — Scouring-rush {Equisetum arvense, Scouriag-rush Family, 

 Equisetacece). 1, spore-bearing shoot mth erect branches ending in 

 cone-like clusters (a) of sporophylls or sporangia-bearing leaves. ^, vege- 

 tative shoot, with underground stem bearing tubers , (a) gorged with 

 food. 3, a sporophyll with sporangia, enlarged. 4. same, showing 

 sporangia split open after discharging the spores. 5, 6, 7, spores with 

 "elaters" wrapping closeUs or more or less spread. (Wossidlo.) — 

 Common in moist places. 



ripe suddenly straightens, so as to rupture the thin wall in front and 

 eject the .spores. Sporangia of this type although differing in many 

 ways from those of the adder-tongue and its kin, are doubtless 

 homologous with them, for students of ferns find a very complete 

 series of intermediate forms connecting the extremes, ^^egetative 



