166 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Found only in the northern portion of the State. On rocks and trees. 
North American distribution essentially the same as that of Nephroma tomentosa, 
though not thus far collected within the United States to the west. Occurs in all 
of the grand divisions except Asia. 
3a. Nephroma laevigata parilis (Ach.) Tuck. Syn. N. A. Lich. 1: 104. 1882. 
Lichen parilis Ach. Lich. Suec. 164. 1798. 
Thallus lobes sprinkled, especially at the margins, with gray soredia and more fre- 
quently darker or even blackish below. 
Said to be thinner and softer than the type. Ours always sterile. 
Collected at Kettle Falls and at Grand Portage. On rocks. 
In New England and widely distributed in British America. Also known in 
South America, Europe, and Asia. 
Family GYROPHORACEAE. 
The family has two genera, Gyrophora and Umbilicaria. If we take into account 
thallus structure and likewise the peculiar disposition of the apothecia, the family is 
sufficiently distinct. Tuckerman did not divide into two genera, but recognized the 
family as consisting of the single genus Umbilicaria, He regarded the family as 
related to the Parmeliaceae and the Physciaceae through the foreign Omphalodium. 
However, the relation is by no means close, as comparison of both vegetative and 
reproductive tracts will reveal. Schneider, on the other hand, sees in the two genera 
of the present family the highest expression of the Lecideaceae and places both 
genera in that family. Yet this position seems hardly tenable, and it does not appear 
that the present family is more closely related to the Lecideaceae, as limited in this 
volume, than to the Parmeliaceae or the Physciaceae. 
In the development of a strong central attaching organ, the umbilicus, and in the 
external appearance and the anatomical structure of the thallus, there is a consider- 
able resemblance to the better developed Dermatocarpons, but when we consider 
the difference in apothecial structure it appears that the relationship here is also 
rather remote. Thus it seems that the family is a very distinct one, whose relation- 
ships are difficult to trace. Perhaps it might have been better to follow Zahlbruckner 
in placing the present family next to the Parmeliaceae, but this disposition is again 
uncertain, and the Lecanoraceae certainly show stronger affinities with the Parme- 
liaceae than does the present family, 
Members of the family can hardly be confused with any other lichens except cer- 
tain Dermatocarpons, and careful study of the thallus structure, and more especially 
of the apothecial characters, will enable one to distinguish readily enough. The 
general character of the thallus structure and the peculiar disposition of the apo- 
thecia are stated in the descriptions of the two genera. 
GYROPHORA Ach. Meth. Lich. xxxr, 100. pl. 2. f. 6. 1803. 
The thallus is foliose and is attached to the substratum by an umbilicus. The 
margin of the thallus may be entire, but is more usually irregularly incised or torn. 
A cellular cortex is developed on all sides. The upper cortex is quite thin, and the 
walls are gelatinized and the cells small. The lower cortex is strongly developed 
and thickened in order to furnish support for the frequently large thalli supported 
only at one point. This last feature is unusual in foliose lichens. The lower cortex 
is, moreover, usually quite uneven in thickness. The medullary tissue is frequently 
rather thin for so large a thallus. The algal symbiont is Cystocoecus. The umbilicus 
isa stem of cortical tissue, supporting the thallus. Or its lower portion is rather a dense 
bundle of hyphze constituting a large rhizoid. From its base long branching rhizoids 
extend into the substratum, The prevailing colors of the upper surface are brown, 
