ANNALS OF NATURAL HISTORY. 



XLIII. — Remarks on Du Petit Thouars's Theory of the Origin 

 of Wood. By Edwin Lankester, M.D., F.L.S, &c* 



The origin of wood has long been a question of difference 

 amongst botanists, and although the increasing attention paid 

 to botany has rendered this subject much more intelligible, 

 yet at the present time the most eminent men are divided 

 upon the subject. In entering upon this question, it will 

 perhaps be better to refer to the generally received views of 

 botanists upon the formation of the tissues of plants, as upon 

 these views the whole matter depends ; and in these obser- 

 vations I shall refer to the last edition of Dr. Lindley's f In- 

 troduction to Botany. 5 Adopting the classification of Meyen, 

 Dr. Lindley divides the primary tissues of plants into five, viz. 

 1. Cellular Tissue {Parenchyma) ; 2. Pitted Tissue (Bothren- 

 chyma) ; 3. Woody Tissue [Pleurenchyma) ; 4. Vascular Tis- 

 sue (TrachenChyma) ; and 5. Laticiferous Tissue (Cinenchyma). 

 These tissues are all of them composed of two primary ele- 

 ments, membrane and fibre, and the formation of the latter 

 can be traced to an organic mucus (vegetable gelatin of 

 Schleiden), supposed to be universally present in or between 

 the cells of growing tissue t° " However different/ 5 observes 

 Dr. Lindley, " these tissues may be from each other, in sta- 

 tion, function, or appearance, there is no doubt that all are in 

 reality modifications of one common type, the simple cell f 

 and the observations of Mirbel on the development of Mar- 

 chantia seem to confirm such a view. Thus while the tissues 



* Read in the Natural History Section of the Meeting of the British As- 

 sociation, Birmingham, 1839, and communicated by the Author. 



f See Schleiden's Beitrage zur Phytogenesis in Miiller's Archiv, No. 2, 

 1838, of which an admirable translation appeared in Part VI. of Taylor's 

 Scientific Memoirs ; also Lindley 's Introduction to Botany, 3rd edition, p. 2 ; 

 and Meyen's Neues System der Pflanzen-Physiologie, 1 Band. 



Ann. Nat. Hist. Vol. 5. No. 33. Aug. 1840. 2 d 



