98 



Mycologia 



ever, station VI contains basalt as well as tuff, and this conclu- 

 sion can not be regarded as secure until several stations composed 

 entirely of tuff are examined. The prevalence of tuff in the 

 present station doubtless accounts for the drier conditions which 

 have given species of Acarospora in greater numbers. 



Station VII is the north face of a basalt block near the Desert 

 Laboratory. The lichens determined from this station are very 

 similar to those from stations I and VI, and a consideration of 

 them would add nothing of value. 



Lichens of Soil and Trees 



At all of the stations an effort was made to find lichens on the 

 soil. At stations II, III, IV, VI and VII nothing was found 

 on the earth, while from stations I and V were found numbers 

 5, 6, 7, 28, 30 and 31. Mr. Blumer stated that the lichens col- 

 lected at station V were found on wet soil, nothing appearing to 

 the eye on dry soil. Inconspicuous lichens are much more easily 

 visible when moist, and this fact may account for the difference 

 in appearance, but Mr. B. E. Livingston has found that the soil 

 becomes air-dry for a considerable depth during dry seasons,* 

 and it is more probable that the lichens of the soil, whose short 

 rhizoids penetrate but a small portion of the distance down to 

 soil moisture in drier situations, are for the most part confined to 

 shaded places where the moisture is retained longer and where it 

 is doubtless drawn upward along the faces and crevices of the 

 rocks extending into the soil, so that the lichens can get more 

 moisture from below than they could get by evaporation through 

 the air-dry layer of soil above the caliche in drier places. A 

 thorough study of the earth-inhabiting lichens of the region should 

 be made, however few may be the number of species found, for 

 the sake of the light that would be thrown upon general ecologic 

 problems. 



The lichen flora of the woody plants of the area must be very 

 limited, for repeated requests for such material brought nothing 

 but a few sterile and poorly developed specimens of a Physcia 

 and a Placodium. These were collected on Parkinsonia micro- 

 phylla, very close to the ground, among rocks on a north slope. 



* Livingston, B. E. The Relation of Desert Plants to Soil Moisture and 

 to Evaporation. Pub. Carnegie Institution of Washington, 8. Au 1906. 



