326 MICROSCOPIC FOEMS OF VEGETABLE LIFE. 



triangular valves (b, c), often curiously marked, whicli enclose a 

 nucleus of a light reddish color; this nucleus is principally com- 

 posed 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 re- 

 volve within the cell ; and at last the cell-wall gives way, and 

 the spiral thread makes its way out (g), partially straightens 

 itself, and moves actively through the water for some time (h), 

 in a tolerably determinate direction, by the lashing action of two 

 long and very delicate filaments with which they are famished. 

 The exterior of the " nucule" (a, b) is formed by five spirally 

 twisted tubes, that give it a very peculiar aspect ; and these en- 

 close 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 cell ; 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 gives origin to a single new plant by a kind 

 of germination. The complete specialization of the Generative 

 apparatus which we here observe (the organs of which it is com- 

 posed being distinctly separated from the ordinary vegetating 

 structure of the plant), as well as the complex structure of the 

 organs themselves, mark out this group, in spite of the simplicity 

 of the rest of its structure, as belonging to a grade very much 

 above that of the other families that have been treated of in this 

 chapter ; but as scarcely any two Botanists agree upon the exact 

 place which ought to be assigned to it, the convenience of asso- 

 ciating it with other forms of vegetation of which the Micro- 

 scopist especially takes cognizance, is a sufiicient reason for so 

 arranging it in a work like the present. 



