DB. M. J. SCHLEIDEN ON PHYTOGENESIS. 305 



root. Here I can contribute but little to the explanation of the 

 subject; for as yet I have not succeeded, in the rather Umited 

 researches that I have instituted, in coming to any satisfactory 

 result ; for 1 found it quite impossible to decide the question, 

 whether there is secreted at the extremity of the radicle a liquid 

 in which new cells are formed. On the other hand, it is certain 

 that there exists in the extremity of the root a concavo-convex 

 group (a meniscus) of cellular tissue in which the process of the 

 formation of cells takes place in the same way as in the ascend- 

 ing parts of the plant. A main cause of the elongation of the root 

 consequently consists in this, — that on the convex side of that 

 cellular mass new cells are constantly formed in the interior of 

 those already present, while on the concave side the cells aheady 

 formed expand cotemporaneously, and generally indeed most 

 predominantly in the longitudinal direction, and thus constantly 

 push the extremity of the root before them. 



The third case, the formation of the accidental organs of the 

 plant, I must here entirely pass over, as I am wholly unfurnished 

 with any personal observations on the subject. Probably, how- 

 ever, the process here is the same as in former cases, for Meyen 

 [Physiology, Vol. i. p. 209,) observed the cellular nuclei in the 

 germinating tubers of Orchideee. Moreover, analogy leads to 

 the same result, since all these parts are nothing more than 

 morphological modifications of organs which have already been 

 previously treated of. It still remains, however, for me to men- 

 tion a fourth point, namely, the increase in thickness of plants 

 forming woody stems (Dicotyledons). The origin and import of 

 cambium is the nut upon which so many young phytologists 

 have already broken their milk-teeth, the Gordian knot which 

 80 many botanical Alexanders have cut instead of untying, and 

 the enigma in the solution of which almost aU the Coryphaei 

 of our Science have laboured with more or less success. My 

 inquiries respecting this layer of distinct origin between bark 

 and wood are by no means concluded. 



Before I proceed, however, to the communication of my ob- 

 servations on this subject, it is requisite once more to take up 

 the question of the individuality of plants. — I have above ob- 

 served, that in the strictest sense of the word, only the simple cell 

 deserves to be called an individual. If we go a step fiu'ther, we 

 might regard each axis with its lateral organs as simple beings. 

 Ifj however, we disregard this composition of the plant of cells 



