Braun and Engelmann's North American Equiseta. 81 



Art. XI.- — A Monograph]/ of the North American species of the 

 genus Equisetum, by Prof. Alexander Braun, of Carlsruhe, 

 Germany ; translated from the author's manuscript, and with 

 some additions, by George Engelmann, M. D., of St. Louis, 

 Missouri. 



My early friend and indefatigable correspondent, Prof. Alex. 

 Braun, having placed in my hands a manuscript monography of 

 the genus Equisetum, full of original views, and offering a very 

 lucid exposition of this interesting genus, I believe I am render- 

 ing a service to the lovers of botany in this country by translating 

 and publishing this paper; to which I add a few remarks of my 

 own, chiefly relating to the two new species of the Western Uni- 

 ted States. • G. E. 



Before we come to the description of the different species, it 

 will be necessary to explain the structure of the stems of the 

 Equiseta, which afford much more characteristic distinctions 

 than their fructification. 



The Equiseta have simple or verticillately branched stems, 

 which are all grooved (amongst the American species only E. 

 eburneum makes an exception, as far as regards the stem, but not 

 the branches) ; they have verticillate leaves, which are connected 

 in sheaths ; their points only being free, and forming what is call- 

 ed the teeth of the sheaths. The carinse, or ridges of the stem, 

 which separate the grooves (valleculce) are either smooth, (E. 

 limosum, E. laivigatum, etc.) or rough from siliceous tubercles, 

 (E. robustum, E. hyemale, etc.) : they are simple, (E. limosum, 

 E. robustum,) or divided by a furrow (sulcus) along their back, 

 so as to form two more or less distinct ridges (E. hyemale, E. 

 variegatum, branches of E. eburneum). In one species (E. scir- 

 poides,) the furrows dividing the carina? become as large and deep 

 as the grooves themselves, so that the apparent number of the 

 carinas is double that of the leaves. 



In all the Equiseta with green stems, (but not in the discolor- 

 ed fertile ones of E. arvense and E. eburneum, or the white ster- 

 ile ones of the latter,) the epidermis of the grooves or valleculas 

 is perforated by stomata. In the first division, these stomata are 

 irregularly distributed over the surface of the grooves (therefore 



Vol. xlvi, No. 1.— Oct.-Dec. 1843. 11 



