SOME OBSERVATIONS ON THE DEVELOP- 

 MENT OF THE KARYOKINETIC SPINDLE 

 IN THE POLLEN-MOTHER-CELLS 

 OF COBJEA SCANDENS CAV.' 



BY ANSTRUTHER A. LAWSON. 



Plates XXXIII-XXXVI. 



From the recent investigations of Strasburger (1897), 

 Farmer (1895, d), Swingle (1897), Harper (1897), Mottier 

 (1898), and others, we learn that centrosomes are present 

 and take an active part in the formation of the karyokinetic 

 spindle in certain of the lower plants. The most complete 

 series of stages yet published showing the behavior of 

 centrosomes in plants is found in the papers of Swingle 

 (1897) and Harper (1897). Swingle investigated the 

 apical cells of Styfocaulon, Harper the developing asco- 

 spores in the ascus of Erysifhe. In both of these cases, 

 when the spindle is about to be developed, there is a body 

 present which is surrounded by a system of kinoplasmic 

 radiations. This body divides into two and the daughter- 

 centrosomes thus formed migrate to opposite sides of the 

 nucleus and form the spindle in much the same manner as 

 in animals. Strasburger (1897, a) has described and fig- 

 ured well defined centrosomes in the oogonium of Fticus, 

 and Mottier (1898) has also found them in the tetraspo- 

 rangia of Dictyota. 



In all of these cases it will be observed that the centro- 

 some is described and figured as taking an active and very 

 essential part in the de^^elopment of the spindle. We have 

 thus a very striking parallel between the formation of the 

 spindle in animals and in the lower plants; but when we 

 attempt to extend this parallel to the higher plants we meet 



1 Contributions from the Botanical Laboratories of the University of Calilornia, No. 3. 

 Presented for the degree of Master of Science. Prepared under the direction of Mr. W. 



J. V. Osterhout. 



[169] November 13, 1898. 



