166 Evans: Hepaticae of Puerto Rico 



If these aberrant forms are removed, the species which are left 

 will fully agree with the characters assigned to the genus 'by Spruce 

 and by Schiffher. In the majority of cases the plants are robust 

 and show a reddish or brownish pigmentation. A prostrate and 

 irregularly branched caudex is first developed, which clings closely 



to the substratum (plate 8, figure 2). From this, secondary 



stems soon arise which are more or less free from the substratum 

 and rarely form rhizoids ; they branch irregularly, many of the 

 branches being subfloral innovations (figure i). Although the 

 branches frequently bear smaller leaves than the stem, they are 

 never truly microphyllous. 



The leaves are imbricated but not densely so, and the lobes 

 spread obliquely or widely from the axis, being more or less fal- 

 cate. They vary in outline from suborbicular to ligulate, the 

 apices are rounded and the margins are entire. The lobules, in 

 their most typical form, are rhomboidal in outline, the keel being 

 straight or nearly so. In some cases about half of the lobule is 

 appressed to the lobe, restricting the water-sac to a narrow linear 

 space along the keel. In other cases the appressed portion is 

 much narrower (figure 2) and may even be absent altogether, the 

 free margin meeting the lobe at a right angle. Under these cir- 

 cumstances the water-sac is relatively larger and the entire lobule 

 may enter into its formation. The free margin is more or less 

 curved and terminates in an apical tooth, which varies from suba- 

 cute to long-acuminate; the sinus beyond is long but usually 

 shallow. The hyaline papilla is at the proximal base of the 

 apical tooth and may be either marginal or slightly displaced to 

 the inner surface of the lobule. Except for the apical tooth the 

 margin is commonly entire. In certain species, however, a second 

 tooth is sometimes developed, proximal in position to the papilla 

 (figure 4). In some cases the secondary stems fail to develop 

 normal lobules (figure i), and it becomes necessary to search for 

 them on the prostrate caudex. The cells of the lobe have firm 

 and pigmented walls and are usually a little convex. The trigones 

 are large and conspicuous, and intermediate thickenings are fre- 

 quent. The trigones are sometimes triangular but it is more 

 usual for them to be triradiate with rounded rays (figure 3). 



The underleaves vary from orbicular to reniform. They are 



