PLANTS OF A SINGLE CELL. 



67 



threads which abound in fresh waters, and are known in some 

 places by the name of Brook-silk. These, under the magnifying- 

 glass, are seen to be single cells, of unbroken calibre, furnished 

 with branches here and there (Fig. 71). The branches are pro- 

 trusions, or new growing points, which shoot forth, and have the 

 power of continuous growth from the apex. In Bryopsis (Fig. 73), 



a beautiful small Sea-weed, the branches are much more numerous 

 and regular : they are often constricted where they join the main 

 stem, if we may so call it, but the cavity continues from stem to 

 branch ; or, in other words, the whole plant consists of a single 

 vegetating cell. 



98. While in these cases the ramifications of the cell imitate, or 

 as it were foreshadow, the stem and branches of higher organized 

 plants, we have in Botrydium (Fig. 70) a cell whose ramifications 

 resemble and perform the functions of a root. This is a terres- 

 trial Alga, with a rounded body composed of an enlarged cell, 

 which elongates and ramifies downwards, the slender branches 

 penetrating the loose, damp soil on which the plant grows, exactly 

 in the manner of a subdivided root. Meanwhile, a crop of rudi- 

 mentary new cells is produced, by original free cell-formation 



FIG. 67 - 69. Botrydium WallrothitMn its development, and with new cells forming within ; 

 after Kutzing: 67, the cell still spherical: 63, pointing into a tube below: 69, the tube pro- 

 longed and branched : all much magnified. 



FIG. 70. Botrydium argillaceum, after Endlicher; the full-grown plant, magnified. 



FIG. 71. Vaucheria clavata, enlarged: a, a spore formed in the enlarged apex of that 

 branch. 72. End of the branch, more magnified, with the spore escaped from the burst apex. 



FIG. 73. Bryopsis plumosa; summit of a stem with its branchlets, much enlarged. 



