170 MOSSES WITH A HAND-LENS 



The plants are green to brownish-green, rather regularly 

 pinnate and of a comparatively large size as shown by the cuts. 



P. PLATYPHYLLA (L.) Lindb., the Common Porella, is found 

 abundantly everywhere and is almost certain to be one of the 

 first half-dozen hepatics to be collected by the beginner. The 

 plants are most commonly collected on the bark of trees, but may 

 be found on logs, rocks, or soil. They are from one to three 

 inches long, 1-3 pinnate with obtuse branches which are closely 

 appressed to the substratum. The perianth is ovoid, narrowed 

 above, denticulate around the inouth. The spores mature in 

 May or June. 



P. PINNATA L., the Pinnate Porella, is also common, but 

 much less frequent than the preceding. It is easily distinguished 

 from the Common Porella by the much narrower and more 

 elongated lobule. It grows on rocks and logs subject to inunda- 

 elongated lobule. It grows on rocks and logs subject to 

 inundation. 



LEJEUNEA. 



The Lejeuneas are tiny plants, our two species being about 

 ■jV of an inch wide. They are likely to be mistaken for the 

 Frullanias, but their lobules are not saclike and show plainly that 

 each is the lower part of the leaf turned under, as each is at- 

 tached to the lobe by its longer edge. The underleaves are 

 unusually large and conspicuous. The Lejeuneas are so much 

 smaller than the Porellas that there is little danger of confusion, 

 but aside from this the difference in lobules noted in the key is 

 very clear and easily made out. The color of the plants is 

 usually lighter than in Frullania or 

 Porella. 



L. CAViFOLiA (Ehrh.) Lindb. is 

 found throughout our- range on trees 

 and rocks. The lobules are inflated so 

 that in dry specimens mounted in water 

 a bubble of air nearly always 

 remains inside. The keel formed at 

 the junction of lobe and lobule is 

 strongly curved and the outline of the 

 FiGuKE 97. Lejeunea cav- leaf is indented at the outer end of 

 from' the under°s?de X e!^"' '^'^ lobule. The underleaves are about 



