﻿3 1 4 BOTANICAL GAZETTE [may 



GENERAL CONCLUSIONS. 



It is quite natural to suppose that the secret of the origin of 

 the cell nucleus can only be revealed by a study of the most 

 primitive types of life. That such a supposition has influenced 

 many investigators becomes quite evident when one glances 

 over the enormous amount of literature that has accumulated on 

 the cytology of the Bacteria and the Cyanophyceae. On these 

 primitive forms a great deal of work has been done with the 

 hope of throwing light on the origin of the nucleus. Through 

 the efforts of Biitchli (1890, 1892, 1896), Fischer (1891, 1897), 

 Zacharias (1887, 1890, 1897), Pella ( 1894) , Macallum (^895, 

 1900), and many others, much valuable data has been accumu- 

 lated, but as yet no satisfactory conclusions have been reached. 

 This failure is probably due to the fact that many investigators 

 have not a correct morphological conception of the nucleus as 

 we find it in the higher types of life. 



As a result of the above studies on the formation of the 

 nuclear membrane, the writer's conception of a nucleus has been 

 considerably modified. Instead of the nucleus being regarded 

 as a sac containing karyolymph, chromatin, nucleoli, linin, and a 

 membrane, the chromatin alone is regarded as the only per- 

 manent morphological constituent of the nucleus. The karyo- 

 lymph and the membrane are merely temporary physiological 

 results. The accumulation of the nuclear sap is the result of 

 protoplasmic activity. It is first secreted within the chromatin 

 mass and later surrounds it. The cytoplasm coming in contact 

 with the nuclear sap forms a membrane in precisely the same 

 manner as it forms the tonoplast when it comes in contact with 

 the cell sap of the vacuole. The writer therefore regards the 

 nuclear sap as no more permanent than the cell sap, and the 

 nuclear membrane as no more permanent than the tonoplast. 

 Furthermore, as we have shown that the nuclear membrane is of 

 cytoplasmic origin, this structure is to be regarded more as the 

 inner limiting layer of cytoplasm than as a constituent of the 

 nucleus. 



To convince one's self that the chromatin is the only perma- 

 nent element of the nucleus, it is only necessary to observe the 



