t 
CELL DIVISION BY FURROWING IN MAGNOLIA 
Clifford H. Farr 
In "Les centres cinetiques chez les Vegetaux" (8), published in 
1897, L. Guignard supported his previous contentions as to the exis- 
tence of centrosomes in Angiosperms by studies on the reduction 
divisions of certain Dicotyledons, namely: Nymphaea, Nuphar, 
Limodorum, and Magnolia. Although most cytologists are unwilling 
to admit that Guignard succeeded in establishing his thesis, yet this 
must be recognized as a very critical piece of work, involving nearly 
one hundred careful drawings which bespeak excellent fixation. His 
figures represent stages in the division of the nuclei, and in addition 
some of those of Magnolia give stages in cytokinesis. There are in- 
cluded in the text a few paragraphs on cell division proper, but most 
emphasis naturally is placed on nuclear phenomena. In some of the 
figures there is shown an equatorial thickening of a few spindle fibers 
following the heterotypic karyokinesis, but other fibers seem to be 
uniform throughout. No reference is made in the discussion to the 
presence or absence of a cell plate. At a little later stage the fibers 
of the central spindle have a twisted, crinkled appearance in the equa- 
torial region for about one third of their length. Meanwhile an equa- 
torial furrow has developed for a short distance centripetally. It is 
shown in all stages of interkinesis to be of about uniform diameter at 
its base and rather sharp at the apex. Just before the nucleoli disap- 
pear in the beginning of the homoeotypic division the furrow reaches a 
depth about equal to the remaining isthmus, and it is said to remain 
arrested there throughout this mitosis. However, Guignard's figure 
25 shows a middle anaphase with the furrow only one half as deep 
as stated. No figures are shown of the completion of the furrow nor 
of cytokinesis of any kind after the homoetoypic karyokinesis. It has 
thus not been fully established that this furrow is related to cell 
division, nor that there is no cell plate involved in the division of these 
cells. Guignard's figures represent the mother-cell wall as thickened 
to about the same extent as is shown by my drawings, although in the 
former it is of more nearly uniform thickness throughout. However, 
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