92 M. Miiller on the Germination of Isoetes lacustris. 



This latter also has now commenced its course of development. 

 It is the cell c in fig. 12, the cell b in fig. 13. It possesses the 

 same characteristics, as mother-cell of the second leaf, as do the 

 mother-cell of the whole embryo and that of the scale. It is a cell 

 with extremely transparent contents and of most delicate con- 

 sistence. The whole future germ-plant is now formed in the 

 embryo. 



1. The first leaf (fig. 12 e) ; 



2. The second leaf (fig. 12/) ; 



3. The scale of the first leaf (fig. 12 c) ; 



4. The future root (fig. 12 b) ; 



5. A reservoir, in which lies stored up the nutriment necessary 

 to the embryo until it becomes capable of supporting itself inde- 

 pendently (fig. 12 a). 



I will treat each of these organs separately in the following 

 paragraphs, in order that I may be able to give a more summary 

 account of them. It is very convenient also to break off here, 

 since we have now arrived at the stage at which the embryo 

 breaks through from the ovule. There are a few words to be 

 added respecting this act. 



The breaking through never happens all at once, but takes 

 place gradually. First the primine bursts (fig. 14 a) ; this is soon 

 followed by the opening of the secundine (fig. 14 b) ; the coat of 

 the nucleus protrudes from these two as a conical process (fig. 14 c). 

 The whole of the upper part of the ovule thus acquires a conical 

 form. 



The primine and secundine persist now in an unaltered condi- 

 tion, till at length, decaying, they fall away, bit by bit, from the 

 coat of the nucleus, which itself in time meets with a similar 

 fate. This now begins to expand considerably. This is caused 

 solely by the expansion, not the multiplication, of its cells. The 

 cellular tissue of the coat of the nucleus thus becomes quite loose 

 in its texture. The papillary cells become less and less conspi- 

 cuous ; all the cells are transparent (fig. 15). 



The result of this is, that as the light penetrates through the 

 expanding coat of the nucleus we see the first leaf, the tissue of 

 which has by this time become green, showing as a little green 

 cone through the upper transparent part of the coat of the 

 nucleus. 



If the entire germ is now extracted from the ovule, it is found 

 exactly of such size that it reaches from the very top of the ovule 

 to the bottom (fig. 15 b). This seems indeed a necessary con- 

 dition, since in order to break through the ovule some pressure 

 must be exerted upon the coat of the nucleus. This pressure 

 can only be effected by the continual growth of the germ in the 

 longitudinal direction, thus becoming longer than the coat of the 



