424 
2 branch short, lobes of the single pair of bracts minutely dentic- 
ulate or entire, the ventral usually acute, the dorsal obtuse, brac- 
teole wide ; perianth broadly obovate from an obconic somewhat 
inflated base, scarcely narrowed above, deeply bilabiate, the lips at 
first subciliate-denticulate, later obsoletely crenulate-dentate or 
nearly entire, strongly revolute, giving perianth the appearance of 
being squarely or obliquely truncate : capsule ovoid, yellowish- 
brown, exserted by about its own length ; spores 50-85 4, echinu- 
late, bright yellowish-green ; elaters 275-325 #x 9-10 #, obtuse, 
2-(3-) spiral. 
Exsicc.: Hep. Bor-Am. 91. 
Hep. Am. 30. 
Can. Hep. 7. 
Common on trunks and branches of trees and more rarely on 
rocks throughout the Pacific Coast from California to Alaska ; as 
far east as Idaho (Leiberg) ; Mexico (fide Gottsche). 
The original specimens were collected by Menzies on the wes- 
tern coast of North America, exact locality unknown. The Euro- 
pean plants referred by some authors to Porella navicularis prob- 
ably all belong with P. platyphylla or P. laevigata. This species 
in a fertile condition can always be very easily distinguished from 
any simulating form of P. platyphylla by the broadly obovate peri- 
anth, scarcely narrowed at the mouth, and by the twice larger 
spores. When sterile, if more obvious characters fail, the numer- 
ous, small, thick-walled cells filling the inferior basal wing of the 
dorsal lobe are of importance ; these are %{—14 the diameter ot 
the cells in the middle of the lobe while in P. platyphylla the cells 
are nearly of a uniform size throughout the lobe or slightly 
smaller at the basal margin. 
7- PoreELta Roetxi Steph. Bot. Centralb. 45: 203. 1891. 
Green or yellowish-brown, usually shining: stems procum- 
bent, rather flaccid, densely depressed-caespitose, 4~8 cm. long, 
subdichotomous below, the primary branches for the most part 
simply and remotely pinnate, branchlets short, often attenuate- 
deflexed : dorsal lobes of leaves densely imbricate, appressed, ob- 
liquely ovate, patent-divergent, .85-1.7 mm. x .6 5-1I.5 mm., apex 
narrowed, subtruncate, obtuse, or most rarely apiculate, inferior 
margin more or less undulate-crisped, the superior repand, cells at — 
