﻿3o6 BOTANICAL GAZETTE [may 



So far as the writer is aware, no observations have been 

 recorded on the origin and formation of the nuclear membrane 

 in plants. It is the object of the present work, therefore, to 

 account for the presence of this membrane and its morphologi- 

 cal relationship to the other nuclear elements, with the hope 

 that it might lead to at least a partial understanding of the 

 morphology of the nucleus itself. 



In undertaking this work it was at first thought that a study 

 of the most primitive types of plant life — -where the cell is 

 much simpler and the nuclear structures less highly differen- 

 tiated than in the higher types- — would be the most natural way 

 of approaching the subject. ' Consequently the cell contents of 

 a large number of forms of the Cyanophyceae and of the simpler 

 Chlorophyceae were examined. A careful study of these forms, 

 however, failed to give satisfactory results so far as the formation 

 of the nuclear membrane is concerned. In the cell of the Cyano- 

 phyceae bodies were found which resembled chromatin, but in 

 non^ of the forms examined could any of the other nuclear 

 structures be identified. These chromatin-like bodies were sur- 

 rounded by neither nuclear sap nor membrane. In the simpler 

 Chlorophyceae examined the chromatin was found to be sur- 

 rounded by both nuclear sap and membrane, but the nucleus 

 was found to be much too small to follow out accurately the 

 stages in the formation of the nuclear membrane. It has been 

 thought advisable, therefore, to use the highly organized nucleus 

 of the flowering plants as an object for this study. The follow- 

 ing conclusions, therefore, are drawn mainly from observations 

 made in the individual history of the typical nucleus of the 



higher plants. 



MATERIAL AND METHODS. 



In order to follow the sequence of events which lead to the 

 formation of the nuclear membrane, it is desirable to obtain 

 material with clear large nuclei, where the various stages in the 

 development of the daughter nuclei may be distinctly observed. 

 For this purpose the sporogenous cells of the higher plants 

 seemed to furnish all the desired conditions. 



Although the spore mother cells of Passiflora coeritlea and the 



