b 



Dixon — Nuclei of the Endosperm of Fritillaria imperialis. 725 



described in this note take place in the embryo-sac simultaneously 

 with normal examples of karyokinesis, and their successive stages are 

 to be found side by side with successive stages of the latter process, so 

 that it seems probable that the same stimuli give rise to these ab- 

 normal divisions as bring about karyokinesis. 



In fixing the material from which the above descriptions were 

 made, the fertilized ovules were taken from fresh ovaries, and dropped 

 immediately into a large volume of alcohol. This material gave 

 excellent examples of normal karyokinesis and of resting nuclei, which 

 exhibited no traces of imperfect fixing, so that I think it improbable 

 that the abnormal divisions can be ascribed to this cause. 



EXPLANATION OF PLATE XXIV. 



All the figures are camera lucida drawiags of nuclei found in the 

 endosperm of Fritillaria imperialis. 



Fig. 1. — Giant nucleus, x 55. 



Fig. 2. — Nucleus breaking into a number of parts. Striae are seen in 

 the protoplasm connecting the severed portions, x 250. 



Fig. 3. — Nucleus dividing by budding, x 250. 



Fig. 4. — Annular nucleus, x 250 



Fig. 5. — Portion of the lining of the embryo-sac after the formation 

 of cell-walls, showing two annular nuclei, the upper one 

 of which is dividing into three, and the lower into two, 

 nuclei, x 75. 



Fig, 6. — Form of nuclear division intermediate between direct and 

 indirect division. Between the two portions of the nucleus 

 a spindle is easily seen, x 350. 



Fig. 7. — Similar to Fig. 6. Showing a very slender connecting piece 

 between the two nuclei, x 350. 



Fig. 8. — Karyokinesis with retarded chromosome, x 350. 



