Aiiicricaii Species of Marchantia. 213 



but is not brought out in the figures of Kny and Miiller. It is 

 sometimes very narrow and absolutely colorless and can then 

 be demonstrated only with difficulty. In the lower series each 

 row is likewise composed in most cases of four cells, those 

 bounding the inner opening being distinctly differentiated. Their 

 usual appearance is clearly shown by Kny (pi. 84, f. 2), each 

 cell being in the form of a narrow, curved, four-sided figure 

 with a rounded median projection extending toward the center 

 of the pore. All the cell-walls immediately bounding the pore 

 are shown covered over with a granular deposit of some resinous 

 substance, which hinders or prevents the entrance of water 

 through the pore. Kny comments on the fact that the pores vary 

 greatly in size and that the projections from the cells bounding 

 the inner opening sometimes meet. In his opinion these projec- 

 tions probably make still more difficult the entrance of water 

 through the pore. This view is upheld by Ruge,^** who finds the 

 pores almost completely closed by the projections in a submerged 

 form of M. polymorpha. In Fig. 2, D-I, some of the variations 

 shown by the cells bounding the inner opening are brought out. 

 In Fig. 2, E, the projections are only slightly developed, although 

 the upper cell on the left approaches tlie condition portrayed 

 by Kny; in Fig. 2, D, F, I, the projections are well developed 

 but not sharply defined from the rest of the cell ; in Fig. 2, G, H, 

 the projections are both well developed and sharply defined. 

 These last figures, drawn from a plant growing in a very wet 

 locality, support the statements of Ruge and agree with the fig- 

 ures published by Miiller. The cells drawn, however, seem to be 

 nearly or quite destitute of the resinous deposit so conspicuously 

 shown in the remaining figures and in Miiller's figures also. 



Although the inner openings of the pores in M. polymorpha -are 

 subject to so much variation, Stephani insists that important 

 specific characters in the genus Marchantia are yielded by the 

 inner openings. He recognizes four types-" and states that they 

 are not connected by transitional conditions. In die first type the 

 four cells bounding the opening are narrow and not materially 

 changed in shape by increased turgidity, the opening itself exhib- 

 iting a quadrate form. In the second t}^pe tlie four bounding 



"Flora 77:294. /. //. 1893. 



"■' Bull. Herb. Boissier 7 : 385. /. a-d. 



