I. W. BAILEY 531 



These facts, as those cited by Chambers, raise the question whether 

 in dealing with cytokinesis we actually are concerned with proto- 

 plasm in liquid or semiliquid phases. 



In any case, this type of cytokinesis, in which the process of cell 

 plate formation is so greatly extended — both as regards space and 

 time — and so clearly dissociated from the usual phenomena of karyo- 

 kinesis, promises upon further and more critical analysis, to be of 

 some significance in any general discussion concerning the dynamics 

 of cell division. 



SUMMARY. 



1. The adjacent, undifferentiated, uninucleated cells of the lateral 

 meristem or cambium are of two distinct shapes and sizes: (1) small, 

 more or less isodiametric initials which are of the same general order 

 of magnitude as the cells of the terminal meristem and embryo ; and 

 (2) large, elongated initials which in certain cases may attain a length 

 of more than 10,000 micra and a volume of 10,000,000 cubic micra. 

 The large initials may be induced to divide to form small initials, and 

 the latter to regenerate elongated cells of normal dimensions. Thus, 

 the cambium affords an unusually favorable medium for the study of 

 a number of fundamental physiological and cytological problems. 



2. A study of the cambium reveals the fact that there is a very 

 much greater variability in the size of meristematic cells in plants 

 than was suspected by Sachs or Strasburger, and that the working 

 sphere of the nucleus is by no means so restricted as assumed by 

 these investigators. 



3. Although the larger cambial initials of Pinus strohus tend to have 

 larger nuclei, the nucleocytoplasmic-relation varies within wide limits 

 and the diploid number of chromosomes is constant. The conditions 

 in the cambium do not support Winkler's view that there is a close 

 correlation between chromosomal number (chromosomal mass) and 

 cell size in the somatic tissue of plants, and that giant cells are 

 hyperchromatic. 



4. The process of cell plate formation in the cambium is a remark- 

 able phenomenon, and one which is significant in discussing the rela- 

 tive merits of various theories concerning the dynamics of kary- 

 okinesis and cytokinesis. 



