140 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
EXPLANATION OF PLATE 22.—Fig. 1, a plant showing the thallusand the apothecia. Fig. 2, a portion 
of a thallus lobe with two apothecia. Fig. 3, a section of an apothecium and the thallus below; @, the 
hymenium, b and c, the hypothecium; d, the inner thallus with hyphe and algal cells; e, the lower 
cortex, thickened below the apothecium. Fig. 4, a section of the thallus; a, the upper cortex; 6, the 
hyphe and algal cells; c, the lower cortex. Fig. 5, a paraphysis and an ascus. Fig. 6, free muriform 
spores. Fig. 7, algal Glaments. Fig. 1, natural size; fig. 2, enlarged about 5 diameters; figs. 3, 4, enlarged 
400 diameters; figs. 5, 6, 7, enlarged 650 diameters. From Schneider. 
KEY TO THE SPECIES. 
Rhizoids conspicuous. 
Lobes wide, rhizoids making a delicate nap......-.-...-- 5. L. myochroum. 
Lobes narrower, rhizoids making a velvety nap.....-.-.. ba. L. myochroum to- 
mentosum, 
Rhizoids not noticeable except under the microscope. 
Margins jagged and fringed. 
Lobes small and densely crowded, ascending and ex- 
panded toward the ends.............-...----.--- la. L. lacerum pulvi- 
natum, 
Lobes as above except larger and less crowded...... 1. L. lacerum., 
Margins undulate, lacerate, or isidioid, but not jagged and 
fringed. 
Upper surface not isidioid or lobulate; margins undu- 
late, but neither isidioid nor lobulate............. 2. ZL. pulchellum, 
Upper surface more or less isidioid granulate or lobu- 
late. 
Thallus lead-colored above, frequently lighter 
below. .............-..2222202--2-222200------ 3. DL. tremelloides. 
Thallus dark lead-colored to greenish or oliva- 
ceous above, scarcely differing below.......... 4. L. chloromelum. 
1. Leptogium lacerum (Retz.) 5. I’. Gray, Nat. Arr. Brit. Pl. 1: 401. 1821. 
Lichen lacer Retz. Fl. Scand. Prodr. 228. 1774. 
Thallus closely adnate, more or less orbicular, middle-sized, 15 to 70 mm. in diam- 
eter, reticulately wrinkled, the many lobes ascending and obscuring the _hori- 
zontal portions, expanded toward the ends, there sinuate and commonly divided 
into finely jagged and fringed margins, olivaceous-brown or more commonly lead- 
colored, scarcely lighter below, for the most part without rhizoids, the thallus 
adhering directly to the substratum; algal cells scattered throughout the thallus, but 
more numerous toward the top, so that algal and medullary layers are not distinctly 
differentiated; apothecia rather rare, small, 0.3 to 1.5 mm. in diameter, subsessile, the 
disk reddish brown and concave or flat, the margin thalloid, but the algal cells fre- 
quently disappearing, giving a biatoroid appearance, paler and entire; hypothecium 
pale; hymenium pale below and brownish above; paraphyses simple or rarely 
branched, commonly enlarged and brownish toward the apex; asci clavate; spores 
pale, ellipsoid, muriformly many-celled, 27 to 48 » long and 11 to 19 wide. 
Generally distributed over the State. On rocks among mosses, 
The plant is widely distributed in North America. Known also in South America, 
Europe, and Africa. 
la. Leptogium lacerum pulvinatum (Hoffm.) Nyl. Syn. Lich. 1: 122. 1858 
Collema pulvinatum Hofim. Deutsch. Fl. 2: 104, 1795. 
Thallus brownish, smaller, and composed of densely crowded and smaller lobes 
with finely fringed edges, giving the plant a more pulvinate appearance than usual, 
Even more seldom fruited than the species. 
A single collection was made along the shores of Snowbank Lake. On humus, 
mosses, and dead pine leaves. Ours is finely fruited. 
