The Development of the Karyokinetic Spindle in Vegetative 



Cells of Higher Plants 



By Amanda McComb 



(With Plates 24 and 25) 



Until recent years very little was known in regard to the 

 development of the nuclear spindle in higher plants. The com- 

 monly accepted view, that the karyokinetic spindle arose through 

 the instrumentality of centrosomes or centrospheres was shown to 

 be incorrect by the researches of Mottier ('97) and Osterhaut ('97) 

 upon spore-mother cells of certain higher plants. This discovery 

 gave an impetus to the study of karyokinesis in vegetative cells, 

 and during the last few years a number of observers have devoted 

 their entire attention to this subject. 



Nemec ('98) who has recently published an account of the 

 origin of the spindle in vegetative cells states, that when the 

 chromatin thread divides into chromosomes a hyaline court ap- 

 pears about the nucleus. In Allium cepa it is never of uniform 

 width around the nucleus, but it is broader on the -sides turned 

 towards the poles of the future spindle. 



This court is sharply differentiated from the surrounding cyto- 

 plasm by a definite membrane. When the chromosomes are 

 assuming an equatorial position this membrane begins to disap- 

 pear. In this hyaline space or court central spindle fibers origi- 

 nate, while the peripheral fibers owe their origin to the membrane. 



"Zu der selben Zeit," to use his exact words, "wo der Kern- 

 faden in die Chromosomen zerfallt, erscheint urn den Kern herum 

 ein hyaliner Hof, der jedoch zunachst an den Polen der Theilung- 

 sachse sicher zu constatiren ist (1. c, Fig. 34, Taf. III.). Der 

 Hof ist gegen die ihn umgebende Plasmaansammlung scharf abge- 

 grenzt. * * * Dasselbe scheint auch seine eigene Membran zu 

 besitzen (1. c, 34, Taf. III.), die jedoch im Stadium wo sich die 

 Chromosomen zur Aequatorialstellung umzulagern beginnen, 



verschwindet." 



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