XIV. 

 STONEWORTS {Chara and Nitella). 



These water-weeds are not uncommonly found in ponds 

 and rivers, growing in tangled masses of a dull green colour. 

 Each plant is hardly thicker than a stout needle,, but may 

 attain a length of three or four feet. One end of the stem 

 is fixed in the mud at the bottom, by slender thread-like 

 roots, the other floats at the surface. At intervals, append- 

 ages, consisting of leaves, branches, root-filaments, and repro- 

 ductive organs, are disposed in circles, or whorls. In the 

 middle and lower parts of the plant these whorls are dis- 

 posed at considerable and nearly equal distances; but, 

 towards the free upper end, the intervals between the whorls 

 diminish, and the whorled appendages themselves become 

 shorter, until, at the very summit, they are all crowded 

 together into a terminal bud, which requires the aid of the 

 microscope for its analysis. 



The parts of the stem, or axis, from which the append- 

 ages spring are termed nodes ; the intervening parts being 

 internodes. When viewed with a hand-magnifier the inter- 

 nodes exhibit a spiral striation. 



In Chara, each internode consists of a single, much- 

 elongated cell, which extends throughout its whole length, 

 invested by a cortical layer, composed of many cells, the 

 spiral arrangement of which gives rise to the superficial 

 marking which has been noted. And this multicellular 



