330 EQUISETACE^E. Equisetum. 



sheath, each tooth representing a leaf. The leaves of the fruiting cone or spike (in 

 several close horizontally divergent whorls) are peltate, 5 - 7-angled, and bear several 

 hood-like sporangia on the inner side. Spores round, furnished with two slender 

 filaments attached by the middle and clavate at the free ends, coiling and uncoiling 

 hygroscopically. Prothallus above-ground, green, often variously lobed, usually 

 dioecious. 



A genus of about 25 species, some with unbranched stems, others with many branches and 

 branchlets, which are verticil lately arranged just below the sheaths of the joints. The ridges of 

 the stem are called carince-, the furrows valleculce, and the hollows beneath them are accordingly 

 carinal or vallecular. The surface of the stem bears minute siliceous appendages in the form of 

 granules, tubercles, rosettes, etc. The furrows are provided with stomata which have inner 

 guard-cells of soft tissue, and outer siliceous cells marked with radiating lines. For a full 

 account of the structure see Sach's Text- Book and Milde's elaborate Monographia Equisetorum in 

 Nov. Act. Acad. Caes. Leop. xxxii, part ii, 1865. 



* Stems of two kinds; the sterile with many slender spreading verticillate 

 branches ; the fertile usually unbranched, pale, appearing in early spring and 

 soon withering. 



1. E. arvense, Linn. Sterile stems rather slender, green and herbaceous, 1 to 

 2 feet high, 6 - 1 9-furrowed ; branches verticillate, very numerous, mostly simple, 

 four-sided, minutely roughened, the lowest joint commonly longer than the sheath 

 of the stem ; fertile stems rarely a foot high, light-brown, the loose scarious sheaths 

 mostly distant, whitish, ending in about 12 brown acuminate teeth : spike rarely 

 over an inch long. Al. Braun, Am. Journ. Sci. xlvi. 83; Milde, Monogr. 218, 

 t. 1-3. E. boreale, Bongard, Veg. Sitch. 174, fide Milde. 



Sierra Nevada ; head of King's River, 7,000 feet elevation (Brewer) ; Clark's Ranch (Torrcy) ; 

 Plumas County, Mrs. R. M. Austin. Common eastward to the Atlantic, and northward to 

 Alaska and Greenland ; also in Europe and northern Asia. There are many variations from the 

 type : sometimes the branches are again regularly branched, and sometimes a fruiting stem will 

 remain through the summer and develop copious branches like those of the sterile stems. 



2. E. Telmateia, Ehrh. Stems stout, often thick as one's finger ; the sterile 

 ones ivory-white or greenish, 2 to 6 feet high, 20 - 40-furrowed, the ridges smooth ; 

 branches verticillate, very numerous, erect-spreading, simple, 4 - 5-sided, the ridges 

 rough and deeply sulcate, the lowest joint shorter than the sheath of the stem ; fertile 

 stems also white, many-furrowed, the loose brownish sheaths very long, often longer 

 than the internodes : spike 1 to 3 inches long. Milde, 1. c. 240, t. 4 - 6. E. fluvi- 

 atile, Smith. E. eburneum, Schreb. ; Al. Braun, 1. c. 84. 



Near San Francisco (Hartwcg, n. 2038) ; San Luis Obispo (Brewer) ; Santa Barbara ( Wood) ; 

 " Redwoods and mountains near Oakland," Bigclow. Oregon and British Columbia, Europe, 

 western Asia, northern Africa, Madeira, etc. Attributed to the shores of the Great American 

 Lakes in various text-books, but probably only through an erroneous label, as pointed out by Dr. 

 Torrey in the Botany of the Mexican Boundary. The verticillately branched stems sometimes 

 produce a fully-developed terminal spike of fructification, constituting the var. serotinum of Al. 

 Braun. 



* * Stems all alike, evergreen, unbranched, or producing a few slender cylindri- 

 cal erect branches : fruit produced in summer. Central cavity of the stems 

 very large. 



3. E. robustum, Al. Braun. Stems tall and stout (sometimes as much as 11 

 feet high and nearly an inch thick), 20 - 48-furrowed ; ridges roughened with a 

 single series of transversely oblong siliceous tubercles : sheaths short, cylindrical, 

 appressed, marked with black girdles at the base, and at the base of the caducous 

 teeth ; ridges of the sheaths tricarinate. Am. Journ. Sci. xlvi. 88 ; Milde, 

 1. c. 532, t. 31. 



Not rare, especially in the southern half of the State, the whole range of the species extending 

 from British America to Ohio, Louisiana and Mexico, and perhaps to New Jersey. Also said to 



