BOT.— Vol. I.] PEIRCE— NATURE OF LICHENS. 235 



cytoplasm in which the large rounded chromatophores are 

 imbedded, is dense, granular and provided with a central 

 homogeneous body of its own which, like nucleoli in 

 general stained with this agent, has a deep red color. 

 Figure 17 shows a gonidial cell in the same section in pro- 

 cess of internal cell-division. For the sake of clearness, 

 protoplasm, chromatophores and vacuoles are omitted from 

 the drawing. Each daughter-cell, though not yet provided 

 with its own cellulose wall, contains a dense, granular 

 central mass, from which the nucleolus-like body is absent. 

 This is what one would expect if the central mass is 

 nucleus, for the nucleoli ordinarily disappear before 

 division, reappearing in the daughter-nuclei only after the 

 lapse of some time. ■' Figure 18 is still another gonidial cell 

 in the same section, which has divided still further, the 

 eight daughter-cells, most of which are below the plane of 

 the drawing, being already surrounded by their own cellu- 

 lose walls and each containing its own central body. 



From these figures, from the behavior of the nucleolus- 

 like body both toward the stain and also in division, from the 

 different staining of the central body, the cytoplasm and 

 the chromatophores, and from its position, as far removed 

 as possible from all the chromatophores, I cannot do other- 

 wise than conclude that it is a nucleus. 



Figures 19 and 20 show the nuclei of a gonidial cell of 

 Usnea sp. (?), and of Sfhcerophoriis glohiferus, respec- 

 tively, dividing and divided. These figures were made 

 from thin microtome sections stained with Anilin-safranin- 

 Gentian-violet-Orange G. The colors, though faint, differ- 

 entiate nucleus and cytoplasm in the manner characteristic 

 of this stain. 



From the evidence it seems to be clear that the gonidia 

 of these lichens have a central nucleus neither remark- 

 able nor different from the nuclei of other similar algse 

 whether within or outside of a lichen thallus; that this 

 nucleus is provided, in the "resting condition," with a 

 typical nucleolus which disappears before the division of 

 the nucleus and the cell; that nuclear division precedes 



