302 HOFMEISTER, ON 



detached without much difficulty. Prom this time however 

 the cells of the surface of its primary axis become more and 

 more closely connected with the neighbouring cells of the 

 prothallium, whilst the latter — in some of which multiplica- 

 tion is continually going on — are more and more com- 

 pressed and at last entirely absorbed by the rapid increase 

 in size of the new plant. 



The end of the secondary axis of the embryo resembles 

 at an early period both in its form and in the mode of mul- 

 tiplication of its cells the terminal bud of a shoot of a 

 developed Equisetum. The comparatively large apical cell 

 and the ladder-like arrangement of the cells of the second 

 degree are clearly distinguishable in the sharply conical 

 wart of cellular tissue (PL XXXIX, fig. 4). As soon as 

 the bud has assumed this form, it produces its first leaf, 

 which like those of the developed plant is a closed, annular 

 sheath of uniform height (a, fig. 4, PL XXXIX). The 

 margin of this sheath is elongated upwards by contempo- 

 raneous division of its cells by means of septa inclined 

 alternately inwards and outwards, and after some time it 

 forms three lobes, which at first are blunt, but soon become 

 pointed (PL XXXIX, fig. 5). 



Contemporaneously with these three pointed processes of 

 the first sheathing leaf the first adventitious root of the 

 germ plant becomes visible. Originating in the multipli- 

 cation of a cell of the inner tissue of the primary axis, it 

 appears at first in the shape of a small, semicircular knob on 

 that side of the embryo which is turned away from the 

 secondary leafy shoot (PL XXXIX, fig. 5). The root 

 grows in length by the multiplication of a cell of the interior 

 of its apex like the root of the developed plant, and pene- 

 trates vertically downwards into the tissue of the prothallium 

 (PL XL, figs. 2, 3). At last it breaks through the latter and 

 makes its way for some depth into the soil. A short time 

 afterwards the upward growing leafy shoot is sent forth from 

 the prothallium. It consists of a small number, from ten 

 to fifteen, of elongated internocles. All its sheathing leaves 

 have three teeth, a rule which applies to Equisetum arvense, 

 JE. pratense, and JE. variegation. 



After the prothallium has sent forth the root and the 



