14 A History of Botany, 1 860-1 goo 



which separate them had led him to formulate his well- 

 known theory of the micellar constitution of all organized 

 structures and of growth by intussusception, the most 

 notable generalization of the time. It had been received 

 with enthusiasm by the leading workers in both anatomy 

 and physiology, and it played a great part in the investi- 

 gations of the earlier years of the period with which this 

 book proposes to deal. 



In France and in Great Britain the condition of know- 

 ledge was not so far advanced as in Germany. Even the 

 mechanics of the stem were wrongly apprehended and 

 gross errors still remained uncorrected. By some of the 

 leading botanists of the day in those countries, cambium 

 was still held to be a jelly-like, mucilaginous substance, 

 out of which new cells were formed by a process something 

 like condensation or crystallization ; the laticiferous 

 vessels of the stem were held to be the path of the descend- 

 ing sap, communicating with the other vessels, and acting 

 as venous reservoirs for the circulating fluid. 



The conception of the vegetable cell which was current 

 in England is especially noteworthy. Cells were said 

 to be formed from a thickened fluid in the interior of cells, 

 or elaborated by their agency, the thickened fluid being 

 called protoplasm. There was no recognition that proto- 

 plasm is the living substance — indeed there seemed a 

 strange indifference to the existence of anything living in 

 the plant at all. In an edition of 1861, Bentley's text- 

 book gave the following presentation of free cell- formation : 

 ' A portion of the protoplasm collects into a more or less 

 rounded or somewhat oval form, with a defined outer 

 border, thus forming the nucleus of the cell ; upon this 

 a layer of protoplasm is deposited, which assumes the 

 form of a membrane, and expands so as to form a vesicle ; 

 on the outside of this a cellulose membrane is secreted 

 and the formation of the cell is completed. The proto- 



