THE FERNS 541 
A 
Fic. 369.—Scouring-rush (Hquisetum arvense, Scouring-rush Family, 
Equisetacee). 1, spore-bearing shoot with erect branches ending in 
cone-like clusters (a) of sporophylls or sporangia-bearing leaves. 2, 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 closely, 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. Vegetative 
