224 Professor Lindley oti the Mode of 



that circumstance alone will be a proof of the plant having been 

 Dicotyledonous, because all other classes are destitute of that 

 central cellular column ; it must, however, always be borne in 

 mind, that absence of pith does not prove that a specimen is not 

 Dicotyledonous, because the roots of those plants have no pith. 

 If a stem is in such a state that nothing can be determined 

 concerning its anatomy, we must then proceed to judge of it by 

 another set of characters. In the first place, it should be in- 

 quired whether it had a distinctly separable bark, or a cortical 

 integument that differed in its organization from the wood with- 

 out being separable from it ; or neither the one nor the other. 

 In the first instance, it would have been Dicotyledonous ; in the 

 second, Monocotyledonous ; in the third, Acotyledonous or 

 Cryptogamic, supposing that it had been a trunk which many 

 successive years had contributed to form. The distinction as 

 appUed to the two latter classes, is not, however, so positive 

 as could be wished, because tree ferns have a cortical integu- 

 ment, but they are easily known by the long ragged scars left 

 by their leaves ; and no other cryptogamic plants possess the 

 character of having, a spurious bark. For this reason, it is 

 doubtful whether Calamnites is related to Equisetaceae, and if we 

 could be sure that the coaly matter found enveloping that genus 

 was really the remains of a cortical integument, there would be 

 no doubt of its affinity being of a different kind, as, for instance, 

 with Juncus. But here is a difficulty ; how are we to be sure 

 that this coaly matter is a part of the original organization of 

 the stem, and that it is not an independent carbonaceous forma- 

 tion ? Another object of inquiry will be^ whether the stem was 

 articulated (as indicated by tumid nodi) or not ; and if the former, 

 whether it had the property of disarticulating ? These circumstan- 

 ces are not of much positive value in pointing out affinities, but 

 they afford negative evidence that must on no account be over- 

 looked. For example, if this had been properly considered in re- 

 gard to Calamnites, although the affinity of that genus might not 

 have been discovered, yet it never could have been referred either 

 to Palms or Bambusas, which, in no instance, ever disarticulate. 

 A third and very important kind of evidence is to be collected 

 from the scars left upon stems by the fall of leaves. Although 

 these will neither inform us of the shape or other characters of 



