Hepaticae : Yale Peruvian Expedition of i^ii. 317 



Apparently the subfloral innovations are invariably of this type 

 (Fig. 7, A; 8, A). In branches of the Frullania type the first 

 underleaf of the branch is either undivided or bifid and is displaced 

 in such a way that the branch seems to arise in its axil. The first 

 leaf on such a branch is rudimentary and very small but the suc- 

 ceeding leaves show normal features. 



The leaves vary from loosely to closely imbricated (Figs. 7, 8). 

 As the plants become dr}^ the lobes tend to assume a suberect position 

 and often wrap themselves around the stem, very much as in Mas- 

 tigolejeunea and Brachiolejeunea. When water is supplied the lobes 

 become more or less flattened out and form an angle of forty-five 

 degrees or more with the axis. In general outline the lobes are 

 ovate and narrow to an acute, obtuse, or even rounded apex; they 

 are plane or slightly convex, and in certain species the postical 

 margin tends to be revolute; the margin is either entire or sharply 

 and irregularly dentate. 



The lobule shows a more or less arched keel and is strongly in- 

 flated, In some cases the inflated portion involves the entire 

 lobule, the free margin being involute except in the region of the 

 sinus, where the opening into the water-sac is situated. In other 

 cases the inflated portion lies along the keel and the free margin 

 is appressed to the lobe. In the various species examined by the 

 writer the free margin has normally borne two teeth, and these 

 may be distinguished as the apical tooth and the proximal tooth 

 respectively, the proximal tooth being situated between the apical 

 tooth and the basal end of the margin. In poorly developed leaves 

 the proximal tooth may be indistinct or even obsolete. The apical 

 tooth is usually large and sharp, being two or three cells long and 

 one or two cells wide at the base (Fig. 7, D, E) ; sometimes the tip 

 cell becomes divided by a longitudinal wall (Fig. 8, G). The hyaline 

 papilla is situated at the proximal base of this tooth but displaced 

 to the inner surface of the lobe, usually two cells from the margin. 

 Beyond the apical tooth the long and shallow sinus extends to 

 the end of the keel. The proximal tooth is invariably shorter 

 and less complex than the apical tooth (Fig. 8, H.). In many 

 cases both teeth bend inward toward the lobe, making it im- 

 possible to determine their true structure without dissection. 

 In certain respects the lobules just described agree in structure 

 with those found in Brachiolejeunea, Ptychocoleus, and Odontole- 

 jeunea. 



The leaf-cells (Fig. 8, F) have thin walls, small trigones, and 

 occasional intermediate thickenings, much more numerous in 



