TABLE OP SPECIES AND VARIETIES. 57 



xxi. PILTJLAKIA, Jjinnteus. 



1. P. globulifera ; Linnaus. The only species. Plate 

 XYIL fig. 2. 



IV. EQUISETACE^. 



xxii. EQUISETUM, Linnceus. 



1. E. Telmateia, Ekrhart. Stems dissimilar, the sterile 



branched, smooth, with about thirty ridges, the 

 fertile simple, short, with large crowded sheaths, 

 and subulate two-ribbed teeth. Plate XX. fig. 2. 



2. E. umbrosum, Willdenow. Stems dissimilar, the 



sterile branched, rough, with about twenty ridges, 

 the fertile simple, with approximate appressed 

 sheaths, having subulate one-ribbed teeth. 

 8. E. arvense, Linn&us. Stems dissimilar, the sterile 

 branched, slightly rough, with from ten to 

 sixteen ridges, the fertile simple, with distant, 

 loose sheaths, having long pointed teeth. 



4. E. sylvaticum, Linnceus. Stems similar, with about 



twelve ridges, and having loose sheaths termi- 

 nating in three or four large blunt lobes; 

 branches deflexed. Plate XX. fig. 3. . 



5. E. limosum, Linnaus. Stems similar, smooth, with 



