262 THE MICROSCOPE AND ITS REVELATIONS. 



individual plant* is effected with considerable rapidity. When these plants 

 are well supplied with nutriment, and are actively vegetating under the 

 influence of light, warmth, etc., they not unfrequently develop ' bulbels,' 

 or 'gonidia,' which are little clusters of cells, filled with starch, that 

 sprout from the sides of the central axis, and then, falling off, evolve the 

 long tubiform cells characteristic of the plant from which they were pro- 

 duced. The CJiaracece may also be multiplied by artificial subdivision; 

 the separated parts continuing to grow under favorable circumstances, 

 and gradually developing themselves into the typical form. 



259. The Generative apparatus of Characece consists of two sets of 

 bodies, both of which grow at the bases of the branches (Fig. 154, A, B) : 

 one set, formerly known as 'globules/ are really antheridia; whilst the 

 other, known as ' nucules,' contain the germ -cells, and are trae pistil- 

 lidia. The ( globules,' which are nearly spherical, have an envelope 

 made up of eight triangular valves (B, c), often curiously marked, which 

 incloses a nucleus of a light reddish color: this nucleus is principally 

 composed of a mass of filaments rolled up compactly together; and each 

 of these filaments (c) consists, like a Conferva, of a linear succession of 

 cells. In every one of these cells there is formed, by a gradual change in 

 its contents (the successive stages of which are seen at D, E, F), a spiral 

 thread of two or three coils, which, at first motionless, after a time 

 begins to move and revolve within the cell; and at last the cell-wall gives 

 way, and the spiral thread makes its escape (G), partially straightens 

 itself, and moves actively through the water for some time (H) in a tol- 

 erably determinate direction, by the lashing action of two long and very 

 delicate filaments with which they are furnished. The exterior of the 

 ' nucule' (A, B) is formed by five spirally-twisted tubes, that give it a very 

 peculiar aspect; and these inclose a central sac containing protoplasm, 

 oil, and starch-globules. At a certain period the spirally-twisted tubes, 

 which form a kind of crown around the summit, separate from each 

 other, leaving a canal that leads down to the central germ-cell or oo- 

 sphere; and it is probable that through this canal the antherozoids make 

 their way down to perform the act of fertilization. Ultimately the nucule 

 falls off like a seed; and the fertilized germ-cell, or 'oospore,' gives ori- 

 gin to a single new plant by a kind of germination. 



DESMIDIACE^) AND DIATOMACE^. 



260. Among those simple AlgcB whose Generative process consists in 

 the ( conjugation ' of two similar cells (235), there are two groups of 

 such peculiar interest to the Microscopist as to need a special notice; 

 these are the Desmidiacece and the Diatomacem. Both of them were 

 ranked by Ehrenberg and many other Naturalists as Animalcules; but 



1 A full account of the Characece will be found in Prof. Sachs's " Text-book of 

 Botany " (translated by A. W. Bennett), p. 278. Various observers have asserted 

 that particles of the protoplasmic contents of the cells of the Characece, when set 

 free by the rupture of their cells, may continue to live, move, and grow as inde- 

 pendent Rhizopods. But the writer is disposed to think that the phenomena thus 

 represented are rather to be regarded as cases of parasitism; the decaying cells' of 

 Nitella having been found by Cienkowski (' Beitrage zur Kentniss der Monaden,' 

 in " Arch. f. Mikr. Anat." Bd. i., 1865, p. 203) to be inhabited by minute spindle- 

 shaped ciliated bodies, which seem to correspond with the * spores ' of the Myxo- 

 mycetes ( 322), going through an amoeboid stage, and then producing a plasmo- 

 dium, which, after undergoing a sort of encysting process, finally ' breaks up * 

 into spindle-shaped particles resembling those found in the Nitella-cells. 



