10 



BOTANY. 



15. In other cases of Division the protoplasm divides 

 itself into two, four, or many parts, which then become 

 spherical in shape. Each part then covers itself with a 

 cell- wall of its own ; and the old cell-wall of the original 

 cell, not being of further use, soon decays or breaks away. 

 This kind of Division is known as Internal Cell-formation. 



16. In the Division of cells the nucleus divides first, 

 after which the cytoplasm separates into two parts. The 

 nucleus usually undergoes a number of curious changes 

 during its division, as follows : {a) the centrospheres sepa- 

 rate and move to opposite sides of the nucleus (Fig. 6, B) ; 



H I J 



Fio. 6.— Indirect division of a cell. ^, before any changes have taken 

 place; B.the formation of chromosomes; C, nuclear disk, and kinoplas- 

 mio spindle; D, splitting of the chromosomes; IS, F, separation of the 

 daughter fibrils : G, polar disks : H, I, J, new nuclei, and division of the 

 cytoplasm, x 600. (From Strasburger.) 



{h) the fibrillar network breaks up into short, V-shaped fib- 

 rils (the chromosomes) which move toward the equator of 

 the nucleus, forming the nuclear disk (Fig. 6, C); (c) the 

 kinoplasm becomes arranged in lines extending from the 

 nuclear disk to the centrospheres, constituting the kino- 



