XIV. 

 STONEWORTS {Chara and Nitclla). 



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^ roof -Ji laments^ and j-epro- 

 dudive organs, are disposed in circles, or ik'/ior/s. 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. 



'i'he 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 Cliara, each internode consists of a single, much- 

 elongated cell, which extends throughout its whole length, 

 invested by a co7iical layer, composed of many cells, the 

 spiral arrangement of which gives rise to the superficial 

 marking which has been noted. And this multicellular 



