138 WEEDS OF THE FARM AND GARDEN 



sori on margin of frond. Found across the continent, also 

 in Europe. 



Horsetail Family (Equisetaceae.) Rushlike herbs with 

 jointed and hollow stem from running rootstocks ; the fer- 

 tile stem, with a conical or spikelike body which contains 

 a shield-shaped body beneath, the spore case, which con- 

 tains the spores ; spore is furnished with two straplike bod- 

 ies called the elaters ; the spores develop into the prothal- 



Fig. 88. Common brake (Pteris aquilina). (Ada Hayden.) 



lus from which the horsetail develops. The family con- 

 tains a single genus, Equisetum, with 25 species. 



Common Horsetail (Equisetum arvense, L.). An an- 

 nual-stemmed perennial producing two kinds of plants; the 

 fertile from four to ten inches high, yellowish brown in 

 color, sheaths eight to twelve-toothed ; the sterile plants 

 slender branched, with four-angled stem and four-toothed 



