I.] MICROSCOPIC PLANTS. 5 



changes must go on in this tiny cell to enable it to 

 build up ks protoplasm and cell-wall out of such 

 seemingly unpromising material; .and perhaps in the 

 course of our microscopical researches we may come 

 across some plants which will throw a little more 

 light upon this subject; but for the present we must 

 bid adieu to Protococcus, and see what else we have 

 under our microscope. 



A long narrow rod, with transparent walls orna- 

 mented with spiral bands of green. It is one of the 

 Yoke-threads orCon- 

 fcrvce, those minute 

 hair-like plants you 



r FIG. 2. 



have so often seen 



in ponds. You observe it is made up of a number 

 of joints; these are cells, each like a protococcus 

 with its sides flattened. The spiral ornament is 

 really the protoplasm so arranged round the interior 

 of the cell-wall. Each cell is capable of sustain- 

 ing life, and giving rise to a new plant. They 

 increase in length by the cells dividing across their 

 width ; they increase in numbers by the protoplasm 

 becoming broken up into many little oval bodies, 

 each provided with two cilia or hair-like appendages, 

 by the constant lashing of which they propel them- 

 selves through the water. When the protoplasm 

 becomes thus broken up, the cell-wall opens and sets 

 them free, each one ultimately becoming a separate 

 plant. It is called the Zygncema, a term which sig- 

 nifies yoke-thread. 



By gently moving our glass slide we become aware 

 of the presence of another of the same tribe of plants 



