182 Upon the Cause of Vegetable Divergence. 



in the passage just quoted. Nay, I would go further, and 

 appeal to any of your readers as to whether or not the greater 

 part of the above extract is anything else than a mere trans- 

 lation of my own observations contained in your Journal for 

 February last ; part of it, in fact, being a tolerably perfect copy. 

 The only point on which the editor of the Edinburgh JoXirnal 

 really differs from myself, is, that he conceives the elasticity 

 of the woody fibre, to be an active agent in causing the seg- 

 ments of a stem to recover their state of rectitude ; whereas I 

 felt inclined to consider it merely as occasionally assisting, but 

 not causing, the recovery of this state ; expressly stating, that, 

 " on removing the piece of stem into syrup, a much denser 

 fluid than sap, exosmosis, for reasons already explained, ensues, 

 the cells become emptied, and the separated portions recover 

 their former rectitude ; the elasticity of the xwody fibre present 

 also, probably, assistiug. ,, Thus, we both admit the existence 

 of elasticity as aiding the segments to recover their state of 

 parallelism, but in different degrees. 



As a proof that the elasticity of wood}' fibre is necessary to 

 the developement of divergence, the case of Fucus palmatus 

 (Rhodomenia palmata) is quoted; this acrogen being made 

 up entirely of vesicular (cellular) tissue, and exhibiting no di- 

 vergence when divided. But this is very far, I conceive, from 

 strengthening the position assumed by the editor of the Edin- 

 burgh Journal ; for it is self-evident that, for the developement 

 of divergence on division, it is absolutely necessary that the 

 cells or vesicles should be of unequal size, and arranged in a 

 particular manner, larger in the axis, and smaller in the 

 periphery of the vegetable structure ; and this not being the 

 case with Rhodomenia palmata, I confess that I should be 

 surprised to find that it, or any other acrogen (especially 

 among the Algaceae) not possessing a distinct axis of growth, 

 exhibit divergence on dividing their fronds. 



I am unwilling to occupy a larger space than necessary 

 with this subject, or I might adduce other arguments in support 

 of the position I have ventured to take. I might ask, In what 

 manner could elasticity be supposed to assist in my 7th expe- 

 riment, in which a piece of the stem of a Stachys was allowed 

 to wither up and dry by exposure to the air, and yet manifested 

 the most complete divergence on dividing it after its cells had 

 been distended with syrup ? Here, I may observe that, if the 

 existence of all xwody [fibre at the circumference, and all vesicidar 

 or cellidar tissue at the axis, of a stem were really necessary for 

 the production of divergence, endogens generally ought not 

 to possess this property, which, however, they really do; of 

 which fact any one may readily be convinced by dividing 



