No. 450.] STUDIES ON THE PLANT CELL. 



It would be interesting if two types of spindle format i( 

 present at opposite poles of the same nucleus and furthe 

 tigation of this subject is much to be desired. The mi^ 

 the central cell of Pinus (Ferguson, :oib, Chambeiia- 

 and Klackman, '98) and Picea (Miyake :03a) show spin 

 mation from accumulations of fibrillne outside of tlu- mu i- 

 without conspicuous polar caps. Still more slrikiii- th 

 irregular spindle of Murrill in Tsuga, described above, 

 Ferguson's (:oia) account of the mitosis in the j^enerat 

 of the pollen grain of Pinus. The spindle here be-ins to ( 

 as a cap-like accumulation of kinoplasm below the niu lens, 

 fibers enter the nuclear cavity and in cooperation \\ ith a 

 reticulum form a system of fibers that extend thiou- 

 nuclear cavity to the inner side of the nuclear mer 

 beyond. This portion of the nuclear membrane persist 

 after metaphase so that one pole of the spindle is found 

 within the nucleus while the other is external and ot r 

 tioned cytoplasmic origin. Coker, : 03, regards the spindle 

 differentiates the nucleus of the ventral canal cell in Tax 

 as almost wholly of nuclear origin and the chromosoi 

 derived largely from the nucleolus. There are evidentl\ 

 interesting complications in this form which deserve t 



It should be noted that whenever spindles are formed 



the fibers have a definite region of attachment from whic 

 extend into the nuclear cavity. Such regions constitute 

 of anchorage for the spindle fibers. In this respect the 

 ©logical side of the process of spindle formation in these 

 is quite similar to that of the animal kingdom and m 

 contrast to other methods that are found in higher plants, 

 will now be considered. 



When spindles are formed after the second methoc 

 by independent fibrillae making up a network around the ni 

 there is an abrupt change in the method ot develo] 

 The kinoplasm ^ becomes distributed around the ' 



such as kinoplasmic caps or centrospheres. 1 her 



