348 HOFMEISTER, ON 



of the formation of the first root, an adventitious one, like 

 all the roots of the vascular cryptogams. Its development 

 commences with the multiplication of a cell of the inner 

 tissue of the embryo, viz., the cell which, lies opposite to 

 the primary cell of the first leaf, and' is separated by a 

 cellular layer from the upper surface of the germ-plant 

 (PI. XL VII, fig. 1). This cell divides, in repeated succes- 

 sion, by transverse septa opposite to one another, forming 

 cells of the second degree, lying alternately above and 

 below the primary cell. The lower ones are produced by 

 the formation of a septum slightly convex below ; their 

 form is that of a meniscus. Their multiplication takes 

 place in two directions only • all the septa which are 

 formed in them are perpendicular to the arched upper and 

 under surface of the cell whose derivative cells constitute 

 one of the cap-shaped cellular layers — enclosed one within 

 the other — which cover the outermost apex of the root, and 

 which, during the growth of the latter, gradually peel off 

 outwardly (PI. XLVII, fig. 3). After the formation of a 

 lower secondary cell, and before the division of the cell of 

 the first degree by a septum opposite to the last-formed 

 septum, septa parallel to the longitudinal axis of the root 

 are produced in the latter cell three times in succession. 

 One of these septa is turned towards the outer side of the 

 root — that side which is turned away from the punctum 

 vegetationis of the germ-plant. The two other septa are 

 at right angles to this one. Thus three lateral cells of the 

 second degree are formed, which are followed by the pro- 

 duction of a shorter upper cell by the division of the 

 primary cell by means of a transverse septum (PL XLVII, 

 fig. 3). I will call the first three the outer, the second the 

 inner of the upper secondary cells. Both kinds of upper 

 cells of the second degree, the lateral cells as well as those 

 which follow them, multiply in all three directions. Their 

 divisions are oftener repeated and last longer than those of 

 the lower secondary cell which belongs to the same period 

 of division of the primary cell. 



The formation of lateral cells of the second degree 

 causes a very considerable unilateral thickening of the root. 

 The diameter of the latter increases much more rapidly on 



