1923] Evans,— Notes on New England Hepaticae,— XVII 93 



may be no signs of apical teeth, and a long series of intermediate 

 conditions may sometimes be found, even on a single individual, be- 

 tween this extreme and a three-toothed apex with sharp teeth sep- 

 arated by obtuse sinuses. The three-toothed condition, however, is 

 rarely realized, most plants showing only one or two teeth, and these 

 may be blunt or otherwise indistinct rather than acute. The leaf-cells 

 average about 27 X 25 \x in the middle of the leaf; their walls are 

 thin, and their trigones are small and often indistinct, usually with 

 straight or slightly concave sides. The cuticle seems to be smooth 

 throughout. 



The underleaves are almost as variable as the leaves. They are 

 distant to approximate and may be slightly imbricate in the vicinity 

 of the shoot-apices. Sometimes they are subappressed, but it is 

 much more usual for them to spread more or less widely from the 

 axis. On well-developed plants they usually measure 0.2-0.3 in 

 length and 0.3-0.45 mm. in width, the shape being broadly quadrate- 

 orbicular. The base is almost straight and shows no indications of 

 auricles; while the straight or slightly bulging sides are usually entire, 

 although vague crenations or sharper teeth may be present in rare 

 instances. The broad and truncate apex may show four rounded or 

 obtuse teeth separated by distinct sinuses. In most cases, however, 

 the teeth are fewer or lacking altogether, the apex then being entire 

 or slightly emarginate. 



Although the perianths of B. denudata are still unknown, female 

 branches with unfertilized archegonia are not infrequent. Branches 

 of this character were detected by Gottsche, who described the 

 involucral leaves as ovate-cordate and crenulate at the apex with one 

 or two teeth. Unfortunately the bracts and bracteoles of B. tricrenata 

 and its allies do not attain their full size and development unless 

 perianths and sporophytes are produced, so that Gottsche 's account 

 must not be accepted without reservations. 



The most striking features of B. denudata are due to the production 

 of caducous leaves and underleaves, and it is very unusual to find a 

 patch of specimens in which this habit is not more or less in evidence. 

 The throwing off of the leaves begins abruptly in most cases and then 

 continues without interruption for a considerable period. Although 

 in all probability the production of these leaves eventually brings 

 the growth of the plant to an end, it is not unusual for an axis to 

 fork two or three times after the caducous habit has been initiated. 



