2 14 Alexander W. Evans, 



cells bulge into the opening in the form of rounded projections, 

 the opening itself showing an outline with four strongly concave 

 sides and four sharp angles; by increasing the turgidity this 

 opening can be almost completely closed. In the third type 

 (which is essentially the same as the pores of Preissia) the four 

 cells likewise bulge into the opening but the bulging portions are 

 more sharply defined and the opening appears in the forrn^ of 

 a four-sided figure with very concave sides but with rounded 

 dilations at the angles ; this opening, which Stephani describes 

 as cruciate, can be completely closed by an increase of turgidity. 

 In the fourth type the opening is very large and bounded by 

 many cells (fifteen in Stephani's figure), each cell bulging into 

 the opening in the form of a longer or shorter cylindrical pro- 

 jection, the opening itself thus acquiring a very irregular outline. 

 To the first type Stephani assigns (among others) M. poly- 

 morpha, M. plicata and M. domingensis; to the second type, 

 Al. disjimcta; and to the third type, M. cepJialoscypha and 

 M. paleacea. The only representa,tive of the fourth type is 

 M. macropora Mitt, of New Zealand. 



Schiffner,-^ however, had already called attention to the danger 

 of placing too much confidence in the peculiarities of the cells 

 bounding the inner openings. According to his account these 

 cells in most species of Marchantia bulge more or less into the 

 opening, the form of which may vary accordingly, and his state- 

 ments would support the view that there was no sharp distinction 

 between the first and second types of Stephani. Even in 

 M. Berteroana, which Stephani would assign to his third type, 

 Schiffner finds only an insignificant modification of the usual 

 condition. He adds that the number of bounding cells in this 

 species, although usually four, may vary from three to six on an 

 individual thallus, and that the walls of the cells commonly lack 

 the resinous deposit found in M. polymorpha. GoebeP- is like- 

 wise inclined to recognize a single type of pore in Marchantia 

 with respect to the inner opening, and he sees no essential dif- 

 ference between Stephani's fourth type and the others. He 

 expresses no positive opinion on this last point, however, because 

 he had no material of M. macropora at his disposal. He con- 

 siders that the pores are plastic structures, subject to modifica- 



'' Nova Acta Acad. Leop.-Carol. 60 : 286. pi. ig, f. 8. 20. 1893. 

 "^ Flora 96: 193. 1906. 



