No. 450.J 



STUDIES ON THE PLANT CELL. 



439 



Kinoplasmic caps which form spindles are probably an evolu- 

 tion from the type of centrosphere that is developed de novo 

 with each mitosis as in Pellia. Such centrospheres by becoming 

 less definite in form and lacking radiating fibers would be called 

 kinoplasmic caps. Indeed the centrosphere so evident in the 

 early cell divisions of the germinating spore of Pellia becomes a 

 kinoplasmic cap in the later mitoses of the older gametophyte 

 (Davis, :oi). 



Spindles developed from kinoplasmic caps are characteristic of 



Fig. 4. — Prophases of Mitosis. «.. Dictyota ; late prophase in spore mother cell, fibers from 

 the two asters with centrosomes have entered nuclear cavity to organize the spindle, chro- 

 mosomes gathering to form the nuclear plate, b, Corallina, early prophase in tetra spore 

 mother cell; two centrospheres, the fibers for.n one having entered the nuclear cavity, 

 chromosomes shown. c,» Pellia, nucleus in germinating spore; spindle fibers from ill 

 defined centrospheres entering nuclear cavity, chromosomes and a nucleolus present, d^ 

 Gladiolus, first mitosis in pollen mother cell ; a multipolar spindle, nuclear wall breaking 

 down at one side and fibrilise entering the nuclear cavity, chromosomes and a nucleolus 

 present. After Mottier and Lawson. 



the mitoses in vegetative tissues, meristematic and other embry- 

 onic regions. They have been especially studied in higher plants 

 by several investigators and for a large number of forms, those 

 most completely described being Psilotum (Rosen, '95), Equise- 

 tum, AUiura and Solanum (Nemec, '98a and '98b, '99b and '99c), 

 Pteris, Ephedra and Vicia, (Fig. 3 /, Section I) (Hof, '98) and 

 Allium (McComb, :oo). The polar caps first appear as accumu- 

 lations of kinoplasm on opposite sides of the nucleus which 

 generally elongates. The protoplasm is granular and although 



