148 THE PHENOMENON OF 



lowermost (adjoining the basilar permanent-cell) becomes 

 a large cylindrical, thick-coated seed-cell, as in Cylindro- 

 spermum, while the following shorter cells, richer in con- 

 tents, are perhaps to be regarded as a second kind of 

 germ-cell.* 



From these examples of less decided and often still un- 

 settled contrast of growth in the rows of cells chained 

 together into filaments, let us direct our attention to cer- 

 tain others, in which the contrast of ascending and 

 descending growth becomes more evident, on the one side 

 by distinct root-formation, on the other by undoubted 

 terminal development of the row of cells (cell-forming 

 apical growth). This condition is exhibited in the sim- 

 plest way, namely, by a filament-stem always single, in 

 Ulothrix and (Edogonium, two genera, otherwise very 

 different, which recent Algology has extracted from the 

 earlier chaos of Confervae. Vlothrix zonata f has active 

 germ-cells, of which 8 16, or in weaker parts of the 

 filament sometimes only four are formed in one mother- 

 cell. These are of longish-ovate form, having four very 

 fine cilia at the anterior pale extremity, and a red vesicle 

 elongated in the transverse direction in the interior, lying 

 at the side, about the middle. After swarming for at 

 most two hours, these germ-cells come to rest, and 

 immediately germinate. The cell then becomes elongated 

 in two opposite directions, growing out in one, into a 

 slender, hyaline, simple (or bifurcated at the point) fixing- 

 root ; at the other, extending cylindrically, and forming 

 the commencement of a green filament-stem. Usually on 

 the second day the first cell divides into two, about in 

 the middle of the upper green end, and thus are produced 

 a lower root-bearing end, dividing no farther, and an 

 upper end which, after growing to not quite twice its 



* It sometimes appeared to me as though the seed-cell, or the so-called 

 manubrium of Rivularia originated by re-fusion of several previously separate 

 cells, analogous to what occurs in Palmogl&a; but I could not attain a com- 

 plete conviction of the truth of this. 



f Vide Kiitzing, ' Phyc. generalis' (1843), t. kxx. (Also Schacht, die 

 Pflanzenzelle/ 1842, p. 120. A. H.) 



