American Species of Marchantia. 219 



The laminar scales are more numerous than the median scales 

 and form a series about midway between the median scales and 

 the margin. They are attached by a much shorter line and 

 broaden out at once into lunulate or ovate structures, rounded 

 at the apex and destitute of appendages. The marginal scales 

 are still more numerous and attached by even shorter lines, but 

 they resemble the laminar scales in lacking appendages and in 

 most other respects. They are situated near the margin and 

 some of them extend beyond. The arrangement of the scales is 

 shown clearly in a figure by Goebel/^ who brings out the fact 

 that the laminar scales are arranged in an irregular row and that 

 the marginal scales are still more irregular in their arrangement, 

 although a linear series is approximated. 



The account of the scales just given is somewhat at variance 

 with the description and figures of Muller.^- According to this 

 author the innermost scales are long and very narrow; they are 

 attached almost longitudinally throughout their entire length and 

 are destitute of appendages. These are said to be borne instead on 

 the scales of the next outer row, which agree in all respects with 

 the median scales as described by Leitgeb. The third type of scale 

 recognized by Miiller includes both the laminar and marginal 

 scales of Leitgeb. An interpretation of the scales, closely agreeing 

 with Mijller's, has recently been published by Massalongo.^^ The 

 present writer, however, has been unable to demonstrate the 

 narrow innermost scales without appendages. According to his 

 observations the statements of Leitgeb are essentially correct. 



The scales in AI. polymorpha, as well as in the other species, 

 are delicate in texture and are sometimes more or less pigmented ; 

 in most cases, however, the pigmentation is of short duration and 

 the scales become bleached and transparent. The cells tend to 

 be wavy and irregular, especially toward the margin (Figs. 7, A; 

 20, C) . The cell-walls are thin, although trigones may sometimes 

 be demonstrated on the marginal scales. Scattered about among 

 the other cells are cells containing oil-bodies (Fig. 20, D) and 

 rhizoid initials, the latter giving rise to tuberculate rhizoids (Fig. 

 20, E). In the appendages rhizoid initials are absent, but cells 

 containing oil-bodies can often be distinguished (Figs, i, 3, etc.). 



*^ Organographie der Pflanzen /. 138. Jena, 1898. 



^^ Rabenhorst's Kryptogamen-Flora 6:17. /. 12. 1905. 



^^Atti R. 1st. Veneto 75:696. pi. 4, f. 12-15. 1916. 



