3o8 Alexander W. Evans, 



and the cupules show conclusively that the species is a Mar- 

 chantia, and the writer would go even further than Stephani did 

 and reduce it to a synonym of M. chenopoda. This conclusion is 

 strengthened by the fact that numerous specimens of M. cheno- 

 poda have been collected in Bolivia by subsequent explorers. 



Although a wide range of variability is assigned to M. cheno- 

 poda, according to the writer's conception of the species, an 

 equally wide range is assigned to M. domingensis and an even 

 wider range to M. polymorpha. The structures which are per- 

 haps most subject to variation are the epidermal pores, the slime 

 cells, the appendages of the ventral scales and the involucres. 

 The male receptacles and the female receptacles in most respects 

 exhibit features of a more constant character. 



In normal and well-developed specimens the pores are unusu- 

 ally large in the middle of the thallus and are only slightly 

 smaller near the margin. In other cases the contrast in size 

 between the median and marginal pores is much more marked; 

 in still other cases even the median pores may be small or medium 

 sized. Corresponding with these differences in size there are 

 differences in the number of cells in the concentric rows around 

 the opening, although the number of such rows is usually seven. 

 The differences in number are found especially in the third and 

 fourth rows of the upper series and in the third row of the inner 

 series. In the fourth row of the outer series the variation is 

 especially great. In small pores as few as four cells may be 

 present, in large pores as many as eighteen cells, and all grada- 

 tions between these extremes are to be expected. In the third 

 row of each series similar but less marked differences are encoun- 

 tered. In the first and second row of each series four cells are 

 normally present although three, five, six, or even seven cells 

 sometimes occur. 



The slime cells vary greatly in number and in distribution. In 

 typical West Indian material they occur abundantly in the epi- 

 dermis, in the walls of the air-chambers, and in the compact 

 ventral tissue of the thallus. In other specimens they are rare in 

 the epidermis or even absent altogether, although still persistent 

 in the walls of the air-chamber and in the compact tissue ; in still 

 other specimens, and this seems to be especially true of mate- 

 rial from Mexico, Central America and South America, they 

 are restricted to the compact tissue, where indeed they may be 



