618 THE EQTJISETUM FAMILY. 



XC. THE EftUISETUM FAMILY. EQUISETACE.E. 



A family consisting of a siugle genus, distinguished from all 

 others as well by the articulate and whorled stems, only resem- 

 bling some of the larger fossil plants now extinct, as by the 

 fructification. 



I. EQUISETUia. EQUISETUM. 



Leafless herbs, with a perennial, usually creeping rootstock, and erect, rush- 

 like, hoUow, and jointed stems, marked with longitudinal strice or furrows, 

 with a sheath at each jomt which encloses the base of the next intei-node, 

 and is bordered with short or elongated teeth, usually as many as the strise 

 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 wood E. 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 

 openmg 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, roUed spirally round the spore when 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 troijical 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 puzzUng. 



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

 and withering before the barren ones appear. 

 Sheaths of the frmtiug stems ifiore than an inch long, with nume- 

 rous 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 has commenced) 3. WoodE. 



Sheaths with short or subulate teeth. 

 Spike very obtuse. 



Striae of the stem, and teeth of the sheaths numerous (usuaUy 

 15 to 20). 

 Branches few in each whorl or none. Stems mostly firuit- 



ing and simUar 5. Smooth E. 



Branches of the barren stems numerous in each whorl. 

 Fruiting stems simple at first, the branches growing out 



afterwards 4. gkadv E 



Angles of the stem and teeth of the sheaths few (rarely more 



tljan 8) 6. JUanh E. 



