BOT.— Vol. II.] OSTERHOUT— AGAVE. 267 



these may be seen, and in cross sections they appear as a 

 sort of central core of the spindle (fig. 30). After the 

 chromosomes leave the equator this central core of con- 

 necting fibres stands out prominently. 



As will be seen in fig. 30, these fibres are connected with 

 each other by small delicate fibres, so as to form a sort of 

 network. It will be remembered that Belajeff (1894) 

 described the spindle of Larix as a network, but his descrip- 

 tion refers to its appearance in longitudinal section. The 

 appearance of the spindle of Agave in longitudinal section 

 would not justify his description. 



Second Mitosis. 

 I. Introduction. 



The cell-plate formation following the first mitosis pre- 

 sents very interesting features which will be fully described 

 in another paper. The migration of the chromosomes to 

 the poles reveals the presence of numerous connecting 

 fibres forming a sort of central core of the spindle. These 

 fibres remain for some time closely compacted and then 

 begin to spread apart until they finally extend completely 

 across the cell. In the meantime the cell-plate has com- 

 menced to form, and as it nears completion, the connecting 

 fibres begin to disappear. Those in the center are the first 

 to go, leaving a peripheral shell of fibres of great regularity 

 and distinctness, which persists for some time. Finally, this 

 in turn disappears, leaving a completed cell-plate extending 

 from wall to wall. 



Coincident with the disappearance of the fibres is the 

 reappearance of the cytoplasm, which begins in the center 

 and extends toward the periphery of the space previously 

 occupied by the spindle fibres. After the completion of 

 the cell-plate it increases rapidly in thickness, especially 

 where it joins the cell-wall, until the condition shown in 

 fig. 17 is reached. 



The daughter nucleus has in the meantime grown to its 

 full size, and presents the appearance shown in fig. 17. 



