1.] MICROSCOPIC PLANTS. 5 
changes must go on in this tiny cell to enable it to 
build up its 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 or Con- 
Jerve, those minute 
hair-like plants you 
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 interiot 
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 cez/za 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 Zyguema, 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 
