No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 385 



a single large nucleolus, and during this process the nuclear 

 sap gradually loses its staining power. He shows that when 

 the nucleolar substance is dissolved in the nuclear sap, and 

 after the cell division, a portion of this substance plays a part 

 in the production of the cellulose walls of the daughter-cells ; 

 but he holds that not all of it is thus consumed, but that the 

 nucleoli have probably some other, as yet unknown, function. 



Mann ('91) introduces a new method of differential nuclear 

 staining : when plant tissues are stained for ten minutes in 

 saturated solution of heliocin in 50^ alcohol, and then from ten 

 to fifteen minutes in a saturated aqueous solution of aniline blue, 

 the nucleolus is red, the rest of the nucleus and the cell blue. 



Macfarlane ('92) constructs the following hypothesis, based 

 on previous observations of his own and of Mann: "We would 

 consider, then, that the nucleolus is the special chromatic and 

 cell center ; that it sends out fine radiating processes — the 

 intranuclear network — which partially fuse externally to con- 

 stitute the nuclear membrane, the interspaces of the network 

 being occupied by nucleoplasm concerned in metabolic change; 

 that radiating continuations of the chromatic substance pass 

 out beyond the nuclear membrane and form a network in the 

 protoplasm, while we would suggest for future proof or disproof 

 that they further may be continued through wall pores to form 

 an intercellular chromatic connection. . , . We would thus 

 view a plant as a group of connected hermaphrodite cells, , . . 

 bound together by a fine chromatic ramification, in the center 

 of which in each cell is the nucleolus." 



Mann ('92) studied the cells of the embryo sac of Myosiirus 

 viininiHS. At the commencement of the conjugation of the two 

 nuclei resulting in the formation of the primary endosperm 

 nucleus, each nucleus contains "a large deeply stained nucleolus 

 enclosed by a very faintly stained nucleolar membrane," and 

 in each nucleus are also one or two smaller globules, which 

 " seem to originate thus : when the nuclei about to conjugate 

 have come in contact, one or two small nucleoli arise by the 

 unequal division of the primary nucleolus. . . . These secondary 

 nucleoli seem to have at first the power of division, but 

 gradually they lose this power and their property of becoming 



