CELL-DIVISIOX 



539 



plant-like structures are thus formed, notwithstanding that every 

 cell is but a repetition of every other, and is capable of living inde- 

 pendently if detached, so as still to answer to the designation of a 

 * unicellular ' or single-celled plant. These different conditions we 

 shall find to arise out of the mode in which each particular species 

 multiplies by binary subdivision ; for where the cells of the new pair 

 that is produced by division of the previous cell undergo a complete 

 separation from one another, they will henceforth live indepen- 



J I 



FIG. 415. Division of the pollen-mother-cells of Fritillaria persica. (From Stras- 

 burger and Hillhouse's ' Practical Botany,' published by Sonnenschein.) 



dently ; but if, instead of undergoing this complete fission, they are 

 held together by the intervening gelatinous envelope, a shapeless 

 mass results from repeated subdivisions not taking place on any 

 determinate plan ; and if, moreover, the binary subdivision always 

 ^ takes place in one direction only, a long, narrow filament (fig. 424, D), 

 or if in two directions only, a broad, flat, leaf-like expansion (G), 

 may be generated. To such extended fabrics the term ' unicellular ' 

 plants can scarcely be applied with propriety ; since they may be 

 built up of many thousands or millions of distinct cells, which have 



nt 



