370 



but sometimes white, in which case the white margin of the teeth is 

 broader : they often adhere in pairs, and are decidedly persistent. — 

 Catkins terminal, either on the stems or on the branches. 



Equisetum variegatum. 



Root creeping, jointed, branched. Stems many, three to twenty 

 inches long, branched at the base and upwards, generally but not in- 

 variably decumbent and filiform, rather brittle, consisting of numerous 

 fluted articulations, half an inch to an inch and a half long. Ridges 

 or furrows five to nine, the former grooved, and both grained as in 

 E. hyemale and E. Mackaii. Sheaths slightly swollen upwards, the 

 upper half black. Lower border of the black waved or toothed, the 

 dentations alternating with the teeth, and, like them, equal in number 

 to the ridges. The teeth are distinct, never adhering, obtuse, some- 

 what ovate, black in the centre, with a broad, white, membranous 

 margin, and tipped with a short bristle, which is either black or white, 

 and more or less deciduous, while the teeth themselves are persistent. 

 Catkins terminal, rather large in proportion to the size of the plant. 



These descriptions are intended to apply to the plants only " as 

 found on the banks and in the bed of the river Dee," and as seen ei- 

 ther with the naked eye or through a small lens. I have endeavoured 

 to exclude everything that could not with propriety be admitted as a 

 specific distinction. The characters which I have given, and which 

 I find to be constant, together with the various circumstances noticed 

 in what follows, have led me to the conclusion that the three plants 

 are well entitled to be ranked as distinct species. I conceive that the 

 main strength of my position lies in the fact, that amidst all the va- 

 rieties of size and shape which each plant presents, the distinctive 

 characters remain the same. The species never shade off into one 

 another, the smallest specimen of the largest species being readily 

 distinguished from any specimen of the other two ; while, on the other 

 hand, the stoutest stems of E. Mackaii and variegatum can at once be 

 recognized as distinct from each other, and from the slenderer stems 

 of E. hyemale. The following additional remarks apply chiefly to the 

 situation, stems, sheaths, catkins and branching. 



Situation. — The three plants are found at various parts along the 

 course of the Dee, within the parish of Banchory, extending over a 

 space of six or seven miles in length. There are three distinct sta- 

 tions for E. hyemale, four for E. Mackaii, three for E. variegatum. 



