38 ON GROWTH AND EXTENSION IN THE VEGETABLE KINGDOM. 



they contain cell-nuclei and granules of different sizes, colourless, 

 or coloured yellow, red, or green ; not unfrequently this colour 

 diffuses itself in the surrounding sap ; the granules also become 

 granules of starch. The pollen sac and the embryo sac are 

 organs quite different from these, and are often generated from 

 simple cells. The organs of generation of algae appear in these 

 simply-organized beings to be simple cells; so also the spore- 

 cases of lichens and fungi. 



There is no doubt that the outer coating of the cell is formed 

 before the inner, and that one layer after another of the cell- 

 matter is deposited, as Mohl has maintained against Hartig. 

 The deposit of the cell-matter is an act of creation, and not a 

 mere precipitate, otherwise it would be quite inexplicable why 

 particular spots remain uncovered by it, and not unfrequently of 

 equal sizes, and at regular distances. Whether the inner mem- 

 brane or the outer cell-membrane is first formed, it is difficult to 

 say. It appears to me that they are produced both at once. In 

 the youngest membranous cells in the root points the iimer mem- 

 brane could already be separated, as also in the full grown ones, 

 except where the parts were too liard. In very compact woody 

 parts it is not easy to detach it ; but the above-mentioned medium 

 employed by Dr. Schultz of Rostock dissolves tlie whole contents 

 of the woody cells, and the outer coating of the cell alone re- 

 mains, showing that the inner membrane has detached itself 

 with its contents. I find this solving medium very good in many 

 cases ; but great care must always be taken in making use of 

 similar means, otherwise the whole mass is rather confused than 

 cleared up. 



I believe that I have examined the cambium in an earlier state 

 than my predecessors. It is a mucilaginous generating sap, from 

 which the parts of plants are produced by an organic crystalli- 

 zation — a form of expression not incorrectly introduced by some 

 physiologists. 



linger, in the Botanische Zeitung for 1847, p. 289, and even 

 earlier than that, has adduced reasons in favour of the increase 

 of cells by division, and specially by the formation of cross par- 

 titions. That such a multiplication occurs in such abnormal 

 plants as algae, is, however, no conclusive reason why it should 

 be so in other plants. This writer has proved with great exact- 

 ness the multiplication of cells in the new layers of wood, whence 

 he concludes that the multiplication takes place by division. 

 But it appears to me that it can be equally well explained by an 

 exuded fluid from which the new cells are formed. I have never 

 met with a clear case of increase of cells by division in phanero- 

 gamous plaTits. 



Spiral vessel? with their varieties, annular vessels, vessels with 



