40 BOTANICAL GAZETTE [yuLy 
while Aristida longiseta, Sitanion elymoides, Stipa comata, S. neo- 
mexicana, Physalis comata, and Ptilora ramosa are found on south 
slopes and crests. 
AUTUMNAL ASPECT. 
Habitat—Physical water: in clay 8.5-10 per cent.; in gravel 
1.5-2.5 per cent. Non-available water: in clay 8.5-10 per cent; 
in gravel 1.5-2.5 per cent. Available water: none in surface soil. 
Rainfall 1.62-4.03°™; av. daily .006°™. Relative humidity: mean 
49 per cent.; range 12-100 per cent. Wind 4.66" per hour. Tem- 
perature: mean 11.6°C.; mean max. 18.8°C.; mean min. 2.7°C, 
range —5.5°—27.2°C.; soil 18-25°C.; soil surface to 4o°C. Light 
duration 60 per cent. Exposure varied, cover open, soil clay to 
gravel. Duration September 15 to November 1. : 
PRINCIPAL species: Artemisia frigida Willd., Gutierrezia Sarothrae (Pursh) 
Britt. & Rusby, (Grindelia squarrosa [Pursh] Dunal), Senecio spartioides Torr. 
& Gray, Chrysopsis villosa (Pursh) Nutt., Chrysothamnus graveolens (Nutt) 
Greene. 
SECONDARY SPECIES: Lacinaria punctata (Hook.) Kuntze, Oreocarya 
thyrsifloria Greene, Eriogonum Jamesii Benth., Aster polycephalus Rydb., 
squarrosa (Pursh) Dunal, Leptilon canadense (L.) Britton, Machaeranthera 
viscosa Nutt., Chrysothamnus_plattensis Greene, Grindelia squarrosa nuda 
(Wood) Gray, Eurotia lanata (Pursh) Mog. 
During the month of August the rainfall decreases markedly, 
and is only slight during September. The temperature at this time 
is as high as at any time during the year, and the result is the rapid 
loss of water by the soil. Although there is still 8-10 per cent. of 
water in clay and 1.5-2, 5 per cent. in gravel, it is doubtful if there — 
is any available water in the surface soil. | 
Although many plants continue to bloom, vegetative growth is 
practically stopped for all annuals and greatly decreased for peren- 
nials. There must still be some available water, but all the annual - 
plants which would ordinarily continue to grow and bloom if sup- 
plied with only a limited amount of water, have dried up at the 
