312 
The Ohio Naturalist. 
[Vol. V, No. 6, 
10. Ptychobranchus phaseolus Hildreth. Ohio, Tennessee and 
Cumberland River systems; peninsula of Michigan; Kansas; 
Arkansas; Indian Territory; Louisiana. 
11. Strophitus edentiilus Say. Entire Mississippi drainage; 
St. Lawrence system and south in streams draining into the 
Atlantic to North Carolina; north in the British possessions to 
Lake Winnipeg; southwest to central Texas; Tyner, Alabama. 
12. Fegias jalnila Lea. Cumberland and Tennessee river 
systems. 
13. Alasmidonta tnincata B. H. Wright. Upper Mississippi 
drainage; Ohio, Cumberland and Tennessee River systems; 
Michigan; Upper St. Lawrence drainage. 
14. Unio gihbosus Barnes. Entire Missippissi drainage; St. 
Lawrence and its tributaries; Alabama River system; southeast 
into Florida; southwest to the Guadalupe River, Texas. 
15. Pleurabema clava Lamarck. Ohio, Cumberland and 
Tennessee River systems. 
16. Quadriila coccinea Conrad. Entire upper Mississi]>pi 
drainage; St. Lawrence basin in various localities. 
KEY TO THE LIVERWORTS RECOGNIZED IN THE SIXTH 
EDITION OF GRAY’S MANUAL OF BOTANY. 
Edo Claassex. 
This key was prepared for the ])urpose of making the work of 
determining the liverworts described in Gray’s Manual more 
easy than it has been heretofore. Other characters have been 
added to the description of the perianth, here and there, that in 
case the perianth is wanting, it may be possible to find the name 
of the genus of the specimen in hand. 
In the archegonial “flower” of the foliose liverworts the ped- 
icel together with the capsule is usually surrounded by three 
envelopes — the involucre, the perianth, and the calyptra. 
The external envelope, called the involucre, is formed by the 
uppermost leaves which surround the base of the perianth. They 
usually differ from the lower leaves by their size and shape and 
are sometimes more or less connate with the perianth. 
The perianth, surrounded by the involucral leaves, is a sac- 
like envelope of oval or cylindrical form. It may be compressed 
or angular, smooth or folded and its orifice may be either entire 
or lobed, dentate or ciliate. Although usually present it is want- 
ing in Gymnomitrium and most of the frondose liverworts. 
After fertilization the capsule is formed in the interior of the 
archegonium and while developing ruptures the upper part of 
the same by the lengthening of its pedicel. The archegonium 
