EQUIStiTACE^E. 1025 



striae or furrows, with a sheath at each joint which encloses the base of 

 the next internode, and is bordered with short or elongated teeth, usually 

 as many as the striae of the stem. These stems are either simple or 

 have at each node, from the base of the sheath, a whorl of jointed 

 branches similar to the stem, but with fewer striae, and always simple, 

 except in the tvood JE. Fructification an ovoid or oblong terminal 

 spike, consisting of several whorls of peltate, shield-shaped, shortly- 

 stalked scales (usually brown or black), under each of which are several 

 (about 6 or 7) capsules, filled with minute spores and opening down 

 the inner side. Under the microscope there will be seen to be attached 

 to each spore at its base 4 thread-like filaments, club-shaped at the top, 

 rolled spirally round thesporewhen moist, uncoiling elastically when dry. 

 The species are not numerous, although widely diffused over the 

 temperate and colder regions of the northern hemisphere, extending 

 more sparingly into tropical countries. Some of them accommodate 

 themselves to a great variety of stations and become very variable. To 

 determine them it is not only necessary to have the fruiting stem, but 

 also to observe whether the plant bears or not barren fronds at the 

 same time, and whether these are similar or dissimilar to the fruiting 

 ones. Accidental variations must also be guarded against. The side 

 branches sometimes bear spikes, or shoots similar to these side branches 

 may arise from the stock, and if gathered alone, without observing the 

 more ordinary state of the stems, may become very puzzling. 

 Fruiting stems, in spring, simple, thick, with long, loose 

 sheaths, and withering before the barren ones appear. 

 Sheaths of the fruiting stems more than an inch long, with 



numerous subulate teeth . 1. Great E. 



Sheaths under an inch, distant from each other, with 



about 8 or 10 lanceolate teeth . . 2. Field E. 



Fruiting stems appearing in or lasting till summer, at the 

 same time as the barren ones, and nearly similar to 

 them. 

 Sheaths with few lanceolate lobes. Branches of the stem 

 again branched at the nodes (in the fruiting stems 

 appearing often after the fruiting lias commenced) . 3. Wood E. 

 Sheaths with short or subulate teeth. 

 Spike very obtuse. 



Striae of the stem, and teeth of the sheaths numerous 

 (usually 15 to 20). 

 Branches few in each whorl or none. Stems mostly 



fruiting and similar £. Smooth E. 



Branches of the barren stems numerous in each 

 whorl. Fruiting stems simple at first, the 



branches growing out afterwards 4. Shady E. 



Angles of the stem and teeth of the sheaths few 



(rarely more than 8) 6. Marsh E. 



