304 ON THE GERMINATION dF CHABA. 



frrce are unequal and irregular, varying in this respect in different 

 individuals, and successive division seems to follow no certain rules as 

 to position and sequence. The disk is divided into a number of 

 interior cells, and a circle of peripheral cells from which roots of 

 ordinary structure proceed (figs. 9, 10, and 17, and r in other figures). 

 The stem-node of the pro-embryo [s on the plates) also originates as a 

 disk- shaped cell. In a very early stage it is higher on one side than the 

 other ; whether so even from the'beginning and before the first division, 

 I leave undecided. The higher side Pringsheim calls the front, and 

 this inequality increases as growth proceeds, whilst the lateral walls 

 on the upper edge of the front side arch upwards. The divisions, 

 which soon commence in this cell and progress very rapidly, originate, 

 according to Pringsheim's description, in the following manner. 

 Three vertical partitions having the same direction as the front sur- 

 face successively appear ; the first in relation to the long axis of the 

 pro-embryo, near the centre of the nodal cell, and only slightly 

 inclined, the second between the first and the arched front, and the 

 third between the latter and the second. The nearer the surface is 

 approached, the more oblique and inclined outwards the walls become, 

 and the third is bent over and fixed in such a way that it cuts off that 

 portion of the upward-arched front that is outside of the cell lying on 

 the lateral surface of the pro-embryo. The latter commences the 

 order of succession of the divisions of the apical cell of a Chara stem ; 

 it builds up the first stem of the plant. The three remaining cells 

 bounded by longitudinal partitions divide by means of excentric, 

 vertical, outwardly concave walls. The cells cut off by this means as 

 peripheral cells, about six in number, may develop into imperfect 

 leaves. 



Pringsheim regards the processes thus described by him in such a 

 light that our third or stem nodal cell of the pro-embryo has the 

 character of an apical cell, or vegetative cell of a stem, having its 

 growing point nearly horizontal and lying in the upward-curved front 

 surface. The three following longitudinal walls successively cut off 

 three segments, which become imperfect nodes, " transition nodes," 

 bearing imperfect leaves, whilst the fourth, which projects over the 

 foreside, develops as the apical cell of the leafy stem. 



^Lccording to Mr. Kamienski's investigation on the development 

 of the root-borne pro -embryos of C. aspera, the results of which were 

 subsequently confirmed by the accessory pro-embryos of C. fragilis^ 

 crinita, and Tolypella glomerata, and the principal pro-embryos of 

 C crinita and intricata, the formation and division of the stem node 

 is essentially different and much simpler. (Pigs. 15, 16, and 19 to 

 26.) The discoid cell is first of all divided by a vertical wall 

 (halving- wall, fig. 19, and others, h), passing through the midst of 

 the front surface, into two nearly equal portions. By successive 

 longitudinal division each of these cells presents a half-circle of 3 or 4 

 pevipherical cells, and one abutting on the halving-wall, forming to- 

 gether two inner cells, in a ring of 6 to 8 cells. The partitions by 

 which the peripherical cells are cut off begin in each half on the fore- 

 side and extend towards the back. The first cell is cut off on one 

 side of the halving-wall, the second on the other, and so on, alterna- 

 ting, and therefore, if numbered according to their order of origin, the 



