THE HIGHER CRYPTOGAMIA. 279 



may have given rise to the opinion that the vascular bundles 

 of the stem of the Equisetacese unite in each node to form 

 a confused mass of tissue.* 



The normal mode of cell-multiplication in the pimctum 

 vegetationis of the adventitious roots is identical with that 

 in Aspidiumfilias-mas. The cell of the first degree, whose 

 continuous division is the cause in the first instance of the 

 growth of the root lies in the interior of the tissue, nearly 

 above the apex of the root. Its form is tetrahedral. It 

 divides by septa of which three in succession are each of 

 them parallel to one of the three lateral surfaces, and of 

 which the fourth forms the surface of a segment of a sphere 

 seated upon the basal surface which is turned towards the 

 apex of the root. In this way sets of four cells of the 

 second degree are formed, of which the three upper, which 

 adjoin the cell of the first degree, take part in the forma- 

 tion of the permanent portion of the root ; the fourth, by 

 its multiplication produces one of the hood-shaped hryers of 

 the root-tap. Soon after its formation four cells, having 

 a quadrantal basal outline, are produced in its interior 

 by a twice repeated division by means of vertical septa. 

 The cells produced by the multiplication of one of the lower 

 cells of the second degree henceforth divide only by septa 

 perpendicular to the basal surface of the mother-cell and 

 consequently to the next adjoining portion of the surface of 

 the root. All the daughter-cells of such a cell of the second 

 degree lie in one place which is curved parabolically ; they 

 form a blunt hollow cone, and the number of these cones 

 which envelope the apex of the root is the same as that of 

 the cells of the second degree directed downwards which have 

 originated in their puncta vegetationis. The oldest, outer- 

 most of them, reaches as far as the place of origin of the 

 root, the younger, inner ones, are gradually less in proportion 

 to their age. The oldest outermost cellular layers of the 

 apex of the root scale off by degrees and become decayed. 



The cell-multiplication of those cells of the second degree 

 which are directed upwards tends much more to the increase 

 of the number of cells in height than in breadth. The lon- 

 gitudinal division of each such, newly formed cell is 

 * See Nageli, ' Zeitscbrift f. Botanik./ Heft 3 and 4, p. 143. 



