THE FLOWER 227 
Where the karyolymph comes in contact with the cytoplasm a 
nuclear membrane is produced. The formation and enlargement 
of the spaces containing karyolymph continue (Fig. 229, L) until 
the chromosomes again become scattered in the form of a net- 
work typical of the resting stage (Fig. 229, I). As the mass of 
chromosomes becomes more and more spread out by the forma- 
tion of karyolymph a new nucleolus makes its appearance. 
Formation of cell walls. As the chromosomes become collected 
at the poles small thickenings are formed on the fibers in the 

Fig. 230. Suceessive stages in the formation of a cross wall between two 
daughter cells in Tradescantia root tip. (x 1300) 
equatorial region. The fibers gradually spread out until the 
sides of the spindles reach the sides of the cell walls, and the 
thickenings grow until they form a membrane across the original 
cell, dividing it into two (Fig. 230). Subsequently new cell 
walls are deposited on the sides of this membrane, the mem- 
brane itself being the site of the middle lamella. 
Individuality of the chromosomes. ‘The number of chromo- 
somes in a nucleus varies greatly with different species but is 
constant for the same species. The chromosomes are believed 
to retain their individuality through the resting stage of the 
nucleus, and so from one cell generation to the next. In other 
words, the same chromosomes that pass to a pole in the ana- 
phase of one division reappear during the prophase of the 
