CENTROSOMES IN PLANTS. 
L. GUIGNARD. 
THERE are few questions in cytology to which so much 
attention has been paid in recent years, especially by zoologist 
as that of centrosomes and directive spheres. First observei, 
as is known, in animal cells undergoing division, they were 
later also found in the same cells in a resting stage. The pres 
ence of centrosomes in plants had not been demonstrated befor 
my investigation of the subject. But, according to recett 
work, instead of being of general occurrence in plants, as We 
believed, they may be limited to the lower groups of the plat! 
Kingdom. However, in a subject so difficult, in which the 
ord of new observations may be expected daily in consequent 2 
of the incessant progress of investigation, I do not believe abso- 
lute assertion of such an opinion is prudent. 
Without entering into details, it will suffice to recall first™®* 
in animal cells the morphological and microchemical character 
one clear toward the center, the other 
wweewe Periphery. Also, it is often poorly defined, 
. refrangibility different from that of the surrounding is 
plasm. The radial striation which usually surrounds it ee 
origin partly in the centrosomes, partly in the central regio?” 
the sphere, | 
ften 1% 
densatio® 
ized # 
[ 
In animal cells in the resting stage the sphere is © 
Ing, Or is indicated only by a slight protoplasmic ¢oP 
around the centrosome. Sometimes it is even disorgan 
158 
