EQUISETACEiE. 79 



showing how effectually microscopic examination corrects some 

 botanical errors, and I trust that you, as microscopists, will 

 pardon the digression. 



Let me now direct your attention to the subject of antiquity of 

 type as manifested in the EquiSETACEiE. I will then conclude 

 with a few parting words on permanency of type as shown in this 

 and some other portions of the vegetable kingdom. Although 

 one or two naturalists of some eminence have expressed a doubt 

 as to whether the Calamites of the Carboniferous period are true 

 Equiseta, there can, I think, be no doubt that representatives of 

 the order not only existed but occupied a prominent place in the 

 Flora of the Coal period. 



Palaeontologists of no mean reputation give the primary repre- 

 sentatives of the Horsetail family a place amongst the earliest 

 traces of land vegetation yet discovered, namely — in the flora of 

 the Old Red Sandstone or Devonian period. PI. XL, Figs, i 

 and 2, represent stems of Calamites found in the coal-beds 

 of Europe. A careful examination of two slides I have lately 

 obtained from Mr. Spencer, of Halifax^one of which contains a 

 transverse and the other a longitudinal section of a species of 

 Calamite found in the Halifax coal strata, has enabled me to 

 form an opinion as to the vascular structure of these giants 

 of the forest and marsh of the Carboniferous era. Calamites had 

 peculiar roots. Fig. 3 is a representation of the radical termi- 

 nation of a Calamite. I think it is not improbable that the 

 transverse section under observation has been taken from some 

 part of the root of a Calamite. The dimensions of the section 

 and other indications seem to point to this conclusion. I once 

 possessed a fossil of a Calamite found in the coal-fields of Derby- 

 shire which measured more than five inches in diameter. 



An eminent French botanist, Adolphe Brogniart, has called the 

 Carboniferous period " the age of Acrogens," so great appears to 

 have been the numerical proportion of flowerless plants of the 

 families of ferns, club-mosses, and horsetails. Brogniart reckoned 

 the known species in 1849 at 500, and the number has been 

 largely increased by recent research, in spite of reductions owing 

 to the discovery that different parts of even the same plants have 

 been taken for distinct species. " Brogniart's generalisation con- 



