90 M. Miiller on the Germination of Isoetes lacustris. 



the figures by comparing the germ-cell, fig. 7 a, magnified fifty 

 times with the ovule fig. 1, or fig. 14 also enlarged fifty dia- 

 meters. 



Under a power of 250 diameters it is distinctly seen that we 

 have no longer to do with a simple cell, but with a mother-cell ; 

 in the fluid within it float some other cells in which the process 

 of development has begun. Magnified 400 times the secondary 

 (daughter) -cells are seen to consist of extremely delicate mem- 

 branes, some of them also containing cj^toblasts (PI. II. fig. 7 b). 

 The second germ-cell which I met with gives us some results 

 with regard to the import of cytoblasts ; the secondary cells are 

 formed from them (fig. 8). Therefore in the first instance the 

 mother-cell must contain merely a chaotic mass of cytoblastema, 

 since fig. 8 speaks in favour of this, where most of the cell-con- 

 tents consist of inorganized material for cells. Then free cyto- 

 blasts are produced out of this (fig. 8 c), and from these finally 

 are developed the new cell-membrane, as is usual in the forma- 

 tion of the cell from cytoblasts, and the cytoblast remains lying 

 on the wall (fig. 8 d). 



When the whole of the cytoblastema of the mother-cell has 

 been converted into secondary cells it forms a compact globular 

 body (fig. 9 a), the cellular tissue of which is composed of many- 

 sided cells compressed closely together, each containing its cyto- 

 blast (fig. 9 b). The mother-cell now acquires an oval shape. 

 If acted on with iodine, it is rendered evident that the membrane 

 of the mother- cell still incloses the whole tissue, for the latter 

 contracts somewhat on account of the iodine, and the wall of the 

 mother-cell thus becomes very distinctly visible as a colourless 

 membrane enveloping the deep brown tissue (fig. 9 c). However, 

 the presence of the mother-cell membrane is not a matter of long 

 duration ; apparently it lasts only up to this stage. Then it dis- 

 appears, but whether by absorption or mechanical agency I have 

 not observed. It may therefore be truly said that the germ is 

 inclosed as in a sac by the mother-cell membrane up to a certain 

 time. As it has often been asserted that this sac-like envelope 

 of the original mother-membrane remains permanently inclosing 

 the entire plant, I was unwilling to leave the above facts uumen- 

 tioned, bearing as they do upon this opinion which has been so 

 violently assailed by Schleiden. 



Tracing the further course of the formation of the delicate 

 germ, we next find the previously oval embryo extended more 

 into a cylinder slightly curved on one side (fig. 10 a). Here, as 

 in the immediately following stages, the cytoblast is still di- 

 stinctly visible on the wall of every cell (fig. 10 6), till in the 

 more independent germ it is gradually decomposed into chloro- 

 phylle. 



