24 MINNESOTA BOTANICAL STUDIES. 
The holdfast is a disc about 1 cm. across, and may be some- 
what lobed at its margin, due to protruding masses of cells that 
are somewhat rhizoid in function, tending to clasp the irregu- 
larities of the substratum. The under surface appears slightly 
rough and pitted. 
The mature stipe is elliptical in cross-section, but not winged. 
It is thicker and rounder at the holdfast, but flattens out into a 
ribbon-like shape farther up, and widens and thickens slightly 
toward the top. The average width at the bottom is 3 mm., 
and at the top 4 mm. It is about 1 mm. thick at the base and 
2to3 mm. at the top. It is tough and coriaceous below, soft 
and fleshy above. 
The laminal portion is usually two-lobed, and is differentiated 
externally from the stipe by a rather abrupt thickening and by 
the fact that it is generally dotted over with the elevated ostioles 
of the conceptacles, giving it a warty appearance. The lamina 
is also more translucent than the stipe. The lamina is wedge- 
shaped; the lobes into which it is divided in its upper half are 
tapering with rounded points. The lamine have the softest 
tissue inthe plant. There are usually lamine in all stages of 
development, on a main branch, from cylindrical stipe-like 
lamine to old, flat, warty, fruiting ones. 
The color of the plant is nearly uniformly light brown, the 
older parts being a little darker, especially the lower stipe. 
The surface, except on the fruiting lobes, is smooth and shining. 
The plant is very elastic. 
Adventitious shoots may arise on any part of the surface of 
the plant. They occur chiefly where old wounds have healed 
over. For instance, where a branch has been torn of, or a 
lamina cut off, or where incisions have occurred, here may be 
found proliferations arising as small outgrowths. Sometimes 
only one may occur, again a dense cluster. Some of these de- 
velop into large shoots. | 
The conceptacles may easily be seen by looking through the 
translucent lamina toward a strong light. They are thickly 
scattered over the lamina and its lobes. There is a rude ar- 
rangement of the conceptacles in rows running approximately 
perpendicularly across the axes of the lobes. There are 150 to 
200 conceptacles on a lamina. They are developed in the 
younger tissue at the ends of the lamina lobes. Hence the 
more mature conceptacles are found some distance from the tip 
