Hepaticae : Yale Peruvian Expedition of igii. 



309 



of about 3 mm., a width of about 1.8 mm. in the broadest portion, 

 and of about 0.5 mm. in the apical region. They are closely imbri- 

 cated and long-decurrent both antically and postically ; when dissected 

 off and spread out they are seen to be ovate-triangular and markedly 

 unsymmetrical. In their natural position they spread widely from 

 the stem, and those on the opposite sides he almost in one plane, thus 

 giving the shoot a flattened ap- 

 pearance. The antical margin 

 is plane in the apical region 

 and often along a part of the 

 decurrent portion, otherwise it 

 is more or less revolute and 

 is usually slightly incurved. 

 Occasionally it bears one or 

 two small teeth in the outer 

 part but in most cases is entire 

 throughout its length. The 

 postical margin is crispate and 

 strongly dilated at the base, 

 spreading backward from the 

 stem at almost a right angle 

 and thus forming a part of a 

 postical crest. Beyond the di- 

 lated portion it extends almost 

 in a straight line to the apex. 

 On robust leaves the dilated 

 portion sometimes bears a series 

 of scattered spine-like teeth, 

 but it is quite entire in many 

 cases, and this condition seems 

 to be the rule on the leaves of 

 branches and of poorly devel- 

 oped stems . Beyond the middle 

 the postical margin bears a few 



scattered teeth. The apex is broad and variously rounded, truncate, 

 or acute, depending somewhat upon the number and position of its 

 scattered teeth. The total number of teeth present on a leaf is 

 usually between five and twenty, the higher numbers being found on 

 leaves where the postical base is spinose-dentate. Most of the teeth 

 are from three to five cells in length. On the perichaeiial bracts 

 the teeth are more numerous, numbering from twenty-five to thirty 

 and are found not only along the whole postical margin but along. 



Figure 4. 



-Plagiochila Guilleminiana 

 Mont. 



A. Leaf, dissected from the stem, X 17. 



B. Cells from the middle of a leaf, X 300. 



C. Tooth from the postical margin of a 

 leaf near the apex, X 225. The figures 

 were drawn from the specimens collected 



at Santa Ana. 



