M. Miiller on the Germination of Isoetes lacustris. 87 



the third, innermost coat with all its contents, but that I distin- 

 guish the coat itself as the coat of the nucleus. 



Regarding the contents, they are the same as those possessed 

 by the ovules of Selaginella. They consist of a quantity of deli- 

 cate, compact, transparent, at least colourless granules, which 

 swim about in a fluid and give this a milky appearance. They 

 are coloured brown by iodine, exactly as occurs in the Selaginella. 

 Originally these cell-contents are but sparing in quantity ; toward 

 the beginning of the germination however they become so much 

 increased that the whole of the cavity of the ovule is filled up 

 (fig. 4). 



3. The Process of Germination. 



The part which the granular cell-contents play in the following 

 process of formation of the embryo is of extraordinary import- 

 ance, at the same time a very simple one. I showed formerly in 

 my ' Essay on the Development of the Lycopodiacese*/ how this 

 granular mass is constantly accompanied by a fluid which presents 

 itself to the observer in the form of globules of oil. I pointed 

 out moreover that these seeming globules of oil consist of a mu- 

 cilaginous substance which furnishes the material for the subse- 

 quent formation of cells, and that these globules, coagulating in 

 iodine and mineral acids, and above all being insoluble in aether, 

 must not by any means be regarded as drops of oil, as has only 

 too frequently happened ; finally that they are the protoplasm of 

 H. v. Mohl. All this holds good also of the contents of the 

 ovule of Isoetes lacustris. In the essay referred to I said further, 

 that, mingled with this granular mass and the protoplasm, we 

 always find some free cells which are coloured blue by iodine, 

 which therefore are amylum-cells. All this is equally applicable 

 to Isoetes. But when I wrote that essay I was still ignorant of 

 the connexion between the granular cell- contents, the amylum- 

 cells and the protoplasm. This has only become clear to me, in 

 the following manner, through the investigation of Isoetes. 



The granular matter is the element of the amylum-cell and 

 the protoplasm. As I have mentioned above, every one of these 

 granules is originally a perfectly compact globule. Such a glo- 

 bule, extremely small in its first stage, gradually increases in 

 diameter, till, arrived at a certain limit, it presents a distinct 

 cellular appearance. A cell of this kind then has the exact 

 aspect of an amylum-cell, to which we readily see, beneath the 

 microscope, that it very closely approaches in weight, since it 

 always sinks to the bottom, and in texture, as it is lamellated, 

 and looks almost as if perforated with a number of holes. In 



* Ann. of Nat. Hist. Ser. 1. vol. xix. 



