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III. — Nematophycus or Prototaxites? 



By William Carruthebs, F.R.S. 



A SEA-AVEED or a conifer? Few vegetable structures, it has been 

 hitherto thought, are better known than coniferous wood, and the 

 last thing likely to be confounded with it would be the tissues of a 

 sea- weed. The merest tyro in histological botany can have made 

 little progress indeed if he cannot at once distinguish the tissues of 

 a cellular cryptogam from the wood cells of a phanerogam. Yet 

 this is the matter in dispute, as indicated by the title of this note, 

 and it is certain that either Dr. Dawson or I have made so little 

 progress in vegetable histology, as not to know such different struc- 

 tures when they are seen. The first stage in a child's literary edu- 

 cation is the acquiring such a knowledge of the alphabet symbols 

 as shall enable him at once to recognize them. The higher flights 

 of reading, composition, and so on, are impossible till the letters 

 are acquired. So in histology, generalizations as to affinities of 

 organisms, made up of particular structures, can only be indulged 

 in by those who know what the tissues are. 



This, then, is the real point to be settled as between Dr. Dawson 

 and myself. The mode of occurrence of the fossil has nothing 

 whatever to do with the matter. It is only and entirely a histo- 

 logical question. Dr. Dawson, from the microscopic investigation 

 of prepared sections of a fossil which he says " presents its struc- 

 tures in a perfection unsurpassed by any fossil wood known to me," 

 has determined that it consists of " wood cells, showing spiral fibres 

 and obscure pores." From the microscojDic investigation of pre- 

 pared specimens of the same singularly-preserved fossil I have 

 determined that it consists of "elongated cylindrical cells of two 

 sizes, interwoven irregularly into a felted mass." It is impossible 

 to reconcile these two descriptions of the same fossil. The two 

 kinds of tissues observed are as different as vegetable tissues can 

 possibly be, as the following tabular contrast shows : — 



Woodcells = Large tubes, or elongated cylindrical cells. 



Fibres = Small tubes, or elongated cylindrical cells. 



Spiral fibres lining tbe inte-'l _ (Hollow tulies external to and fitting toge- 

 rior of the wood cells ../""( ther the larger tubes. 



Wood structure = Ttla contexta. 



I'rututaxites, Dawson ! . . = JWrnatuphycus, Carruthers ! 



These two very different views of the same object are shown in the 

 drawings published by Dr. Dawson and myself. That I might 

 accurately represent Dr. Dawson I included two facsimiles from his 

 figures in my paper.* These may easily be contrasted with the 

 plates accompanying that paper. Both drawings cannot possibly 



* 'Mou. Micr. Jouru.,' Oct. 1872, pp. IGI and IG7. 



