May, 1906.] 
Key to Liverworts. 
537 
2. Midrib covered above and below with 2 rows of enlarged cells; 
hairs very long, divaricate and hooked— deflexed, the marginal 
in twos, rarely with discoid tips. hamata Lindb. 
Alidrib covered above with 2 rows of enlarged cells and below 
with 3—7 rows of cells. 3. 
3. With 3-7 (usually 4-6) rows of cells below, smaller than the upper 
ones and often indistinct; midrib densely pilcse beneath, hairs 
rather long, straight cr nodding, the marginal mostly in clus- 
ters of 3-6, some of which have disccidal tips. 
rnyriopoda Litidb. 
With 3-6 rows of enlarged cells below; hairs rather long, straight, 
divaricate, the marginal usually in twcs, very often disk- 
bearing. conjugata Lindb. 
Mylia S. F. Gray. 
Stem erect, nearly simple, radiculose; leaves orbicular, purplish; 
perianth ov’al; calyptra finally long-exserted. 
Taylori .S. F. Gray. 
Nardia S. F. Gray. 
1. Perianth exserted , connate with the involucral leaves, subcampan- 
ulate and open, deeply laciniate, 6-10 plicate; rootlets purple. 
fossornbroiiioides, Lindb. 
Perianth connate at base with the inner involucral leaves and some- 
what surpassing them, 3-8 carinate, the mouth constricted; 
rootlets whitish reddish or purple. 2. 
2. Marginal leaf-cells quadrate and much larger than the others; 
rootlets whitish. crcniilata Lindb. 
Marginal leaf-eclls about as large as the others. 3. 
3. Branch leaves ovate or obovate, scarcely decurrent, half as large 
as the obliquely semi-circular ( r broadly ovate, decurrent 
stem leaves; fruit unknown. biformis Lindb. 
Branch leaves similar to the stem leaves; fruit known. 4. 
4. Rootlets reddish (claret-colored); leaves roundish oval; involucral 
leaves clcsely appressed and connate with the lower third of 
the perianth, which is slightly exserted, obovate and narrowed 
to the 4-cleft mouth. hyalina Carring. 
Rootlets purple; leaves orbicular; involucral leaves connate (more 
or less) with the small, subobovate perianth, which is slightly 
or not exserted, rooting at base and triquetrous above, but 
becc ming 4— 7 plicate. cremdiformis Lindb. 
Notothylas Sulliv. 
Thallus 5-1.5 mm. wide; capsule with a suture on each side; spores 
light yellowish-brown. orbicularis Sulliv. 
Thallus small; capsule often without suture; spores dark-brown, 
a half larger. mclanospora Sulliv. 
Odoutoschisma Dumort. 
Underleaves mcstly wanting; perianth subulate-fusiform, lacinate 
or cliiate; among messes. Sphagni Dumort. 
U^nderleaves broadly oval, entire and sub-denticulate; perianth 
close-connivent above at length bursting irregularly; on rotten 
wood. dcniidata Lindb. 
Pallavicinia S. F. Gray. 
Fruit arising from the costa, at first terminal, becoming dorsal; 
capsule cylindric, about 5 times longer than broad; involucre 
cup-shaped, short-lacerate. Lycllii S. F. Gray. 
Pellia Raddi. 
1. Thallus indistinctly ccstate, lobed and sinuate. Calyptra much 
longer than the involucre. Antheridia at the base of the in- 
volucre on the same thallus. cpiphylla Raddi. 
