254 W. HOPMEISTER ON THE DEVELOPMENT OF ZOSTERA. 



and lateral borders (PL VIII. figs. 32, 35-3?). The lateral borders 

 at the same time curve over the anterior surface, so that they finally 

 enclose, like a hood, the secondary leaf-bearing axis attached 

 upon that surface. The multiplication of the cells, very active 

 at all the edges of the cellular plate, lasts longest at the upper 

 margin, directed towards the micropyle. The large cell, to which 

 the embryo was previously suspended, becomes pushed very 

 much to one side by this (fig. 32). Soon compressed by the 

 further increase of size of the primary axis, it is in a short time 

 lost sight of altogether. 



The leaf-bearing axis, the lower, naked portion of which 

 has meantime been extending upward with a considerable cur- 

 vature, unfolds, soon after the protrusion of the first leaf, the se- 

 cond, opposite to that ; the third becomes opposed to this higher 

 up on the stem, and finally the fourth to the third (fig. 39). The 

 greatly prolonged extremity of the stem grows by continued 

 repetition of division of the single apical cell, by means of septa 

 inclined alternately to the two surfaces of the leaf, division of 

 the cells of the second degree by radial longitudinal walls, and 

 so on ; corresponding to the rule of cell-multiplication in the 

 rudiment of the fruit of Mosses, of the Marchantiece, the stem 

 of Mosses, the stem of 'the Polypodiaceae, the axes of the 

 Equisetaceae and Pilulariete, and the young embryos of the 

 Coniferae. But, as in the Coniferae, the rule of cell-formation 

 changes subsequently, after the germination of the seed. The 

 one apical cell of the now obtuse, flattened terminal bud (fig. 40) 

 divides by walls inclined successively to the four points of the 

 compass, in agreement with the rule of cell-multiplication in the 

 further developed rudiment of the fruit of Anthoceros*. 



Buds appear in the axils of the older leaves even before the 

 maturity of the embryo. Subsequently also, in the fully-deve- 

 loped, annual sterile plant, the formation of an axillary bud 

 follows that of the leaf almost immediately (PL VIII. fig. 40). 



In the foregoing I have called the cellular body, formed by 

 the increase of the lower segment of the impregnated germinal 

 vesicle, which is finally transformed into a hood-shaped layer of 

 cellular tissue, the axis of the first rank, of the embryo. Older 

 botanists regarded it as the cotyledonary leaf, a view which 



* See page 6 of my Fergleichende Untersuchungen, &c. Leipsic, 1851. 



