io6 PLANT LIFE. 



assume a blue colour ; a very fine large nucleus is also 

 present in each cell, suspended in the sap-cavity by strands 

 of protoplasm, which spring from the parietal layer. If a 

 few filaments are placed in water in a watch-glass, and a 

 small amount of watery solution of eosin, to which a drop of 

 acetic acid has been added, be mixed so as to give to the 

 water a very pale rose colour, at the expiration of half an 

 hour or less the nuclei will be found stained a brilliant red, 

 the remaining portions being unstained. 



In Zygnema the chlorophyll forms two stars in each 

 cell. 



The sexual method of reproduction is by conjugation, and 

 generally occurs in the following manner. Two distinct 

 individuals lying side by side send out lateral prolongations 

 from their cells on the sides opposite to each other, these 

 prolongations from the cells belonging to distinct plants 

 meet, the whole structure now presenting the appearance of 

 a ladder, the sides being formed by the two filaments, or 

 plants, and the rungs by the transverse outgrowths from the 

 opposed cells. On account of the ladder-like arrangement 

 formed by the two plants, this method has been termed 

 stalariform conjugation. During the development of the 

 lateral outgrowths from the cells, the whole of their proto- 

 plasmic contents contract, and a passage being formed 

 between the pair of conjugating cells, owing to the^absorp- 

 tion of the wall at the point of contact of the two lateral out- 

 growths, and the contracted portions of protoplasm from all 

 the cells of one plant pass through the tube formed by the 

 outgrowths, and blend with the masses of protoplasm that 

 have remained stationary in the cells of the other plant. 

 When the union of the two portions of protoplasm is com- 

 plete a cell- wall is formed, the resulting zygospore usually 



