18 BOTANICAL GAZE?PTE [JULY 
15 hours at a distance of 10°. The Hefner-Alteneck lamp burning 
acetate of amyl was used as a standard. The diameter of the wick — 
was 8™™ and the height of the flame was 40™™. The shade pro- 
duced on the Solio paper was used as a standard and copied in per- — 
manent colors. Strips of the same sheet of Solio used to make the — 
standard were exposed and the time required to produce the standard — 
tint recorded. This gave mathematical data and a very simple 
means of comparing light intensities. The light at the June solstice — 
was about 4.5 seconds. All exposures were made parallel to the 
soil surface. 
In the diagnosis of the habitat I have given the figures found — 
to apply during the time studied. Rainfall, temperature, wind, — 
and humidity are averaged for four seasons. The data in water a 
content are based on a single season’s work, but on a great many _ : 4 
readings. The data on non-available water were obtained by 2 : 
taking the soil samples at the time when the plants were dying. — 
This water varies not only with the species, but also with the indi- ae 
vidual plants. The data as collected were largely at the time of — ay 
the dying of Boebera papposa, Salvia lanceolata, Helianthus annuus, — 
Verbesina encelioides, and Solanum rostratum, mostly during the : 
latter part of the aestival period; and these results are given in 
the other diagnoses, since at other times it was impossible unde 
natural conditions to obtain such data. Available water is expressed — 
- in grams to Ioo grams of dry soil. The duration of each aspect, 
as well as many of the factors which are definitely stated, varies from | 
year to year. : 
eee a” 
The species lists are arranged to give an idea of the relative impor- 
tance of the species under each heading, the most important species 
appearing first. The lists without the species in parentheses are A 
for the Mesa region only. Important species of the formation which 
do not occur in the Mesa region are included in parentheses. They 
will be taken up under the general discussion. In the lists impor- 
tant parasitic fungi mcsig ee appear after the species upon which ~ 
they occur. 
Within the formation the following are the terms applied to 
the plant associations: consocies, or areas which are dominated by 
_ a facies of the formation and which at all periods give the character : 
