Spore-pollen samples comprising the Coso flora have been secured at 6 localities. Four of them occur in the type region of the Coso formation near Haiwee Reservoir: Haiwee Reservoir, Darwin Summit, Crowley Point and Panamint Springs. The best exposures of the Coso Formation are in the type area on the west flank of the Coso Range east of Haiwee Reservoir, approximately 10 miles southeast of Olancha, California.

The Haiwee florule was recovered from the type area of the Coso Formation on the east side of Haiwee Reservoir in the foothills of the Coso Range. The locality crops out in the bank on the south side of Cactus Flat Road, in the southwest quarter of Sec. 12, T.20S., R.37E, at an altitude of 4,400 feet (Haiwee Reservoir quadrangle, 1951 edition).

The Coso has yielded a mammalian fauna of Blancan age (Schultz, 1937). Situated 5 miles north of the spore-pollen locality, it has nearly the same stratigraphic position.

The 37 plants representing this florule from the finer brown siltstones in the lower third of the Coso formation include, 14 conifers (Bigtree and Bristlecone Pine, from 1 and 10 pollens, respectively); most abundant conifers were Jeffrey Pine (17) and Incense Cedar (13). 129 pollens studied represent the 37 species of plants.

This flora comes from a desert region, the area being in the transition from the Great Basin to the Mojave Desert. By contrast, most of the species in the fossil flora are regular members of the Sierran pine-fir forest that characterize the west flank of the range northward. The flora includes 2 willows, one alder, one birch, 2 oaks, black walnut, zelkova, 4 species of Ribes, Amelanchier, Holodiscus, Fremontia, Garrya sp, 2 Ceanothus species, Cornus, and Sambucus.

Judging from the climate relations of the plant communities represented in the Haiwee florule, annual precipitation was near 35 inches, whereas it is now only 3-5 inches. It is also evident that winter and summer temperatures were more moderate in the Haiwee area than they are today. Extreme summer temperatures at Haiwee regularly reach 110 degrees F, but in the Sierran forest, typified by Abies, Pinus, Libocedrus, Pseudotsuga, Sequoiadendron and their regular associates, they rarely exceed 85 degrees F; in areas where the modern forest reaches best development, it rarely falls below 10 degrees F, and then for but brief intervals. That conditions may have been somewhat milder when the Haiwee florule as living is suggested by the presence of Coast Forest species the assemblage.

The Late Pliocene Coso sediments, which are locally up to 200 feet thick, overlie the granitic and Paleozoic basement unconformably. On the north-facing hillslope immediately south of State Highway 190 and 1 mile west-northwest of the Darwin turnoff (Darwin Quadrangle, 1951 edition) a section was measured. Not well exposed. The spore-pollen flora was recovered from the finer sandy tuff near the top of the section, about 6 inches below the basalt contact. This flora includes only 13 species, all of which are rare. As compared with the other localities, the poorer representation of fossil grains at this site seems owing chiefly to the coarse sediment, the finer not being represented here; 17 pollen grains found, representing 13 species, only Symphoricarpus had more than 1 grain represented, with 5.

This florule collected from a region now desert, represents an intermingling of species from the Sierran forest with conifer woodland ( 3 species of pine--Bristlecone, Ponderosa and P. monophylla), bigtree, juniper, incense cedar, 1 willow, 1 birch, 1 Ribes, 1 Ceanothus, 1 Cornus, Symphoricarpus, and 1 lingnut. It is apparent that whereas now rainfall at the locality is on the order of 3-4 inches today, the fossil flora resembles vegetation now found in areas where precipitation is approximately 30 inches.

The Crowley Point florule comes from sediments exposed along State Highway 190 at an altitude of 3,880 feet, 0.65 mile south-southeast of Crowley Point Lookout, in the northern part of Section 28, T.18S, R.41E. (Darwin Quadrangle, 1951 edition).

The spore-pollen sample was secured from the finest sandy beds in the upper part of the section, 6 inches below the basalt and just above the road.

The 35 species comprising this florule, which lies on the upper, east slope of the Argus Range near Crowley Point, include 5 pines (Bristlecone from 1 grain; 2 junipers); one cottonwood; two willows; one oak; one elm; two Ribes; one Mahonia; one Cercocarpus; one Rosa; one Fremonitia; two Ceanothus; one Rhamnus; two species of Cornus; and one Symphoricarpus. 67 pollen grains were studied.

Recovered from a region now desert, this flora differs greatly from that at the site today. Most of the species are regular members of the Sierran pine forest and the majority occur on both the eastern and western slopes of the range.

Judging from the present occurrence of the modern species that are similar to those in the flora, rainfall in the Crowley Point area was near 25-30 inches, as compared with 3-4 today. It is also apparent that summer temperatures were much lower than those now occurring on the east slope of the Argus Range, where the extremes often exceed 115 degrees F, as compared with about 95 at the lower margin of the Sierran forest.

This Coso florule come from a section exposed 0.6 mile west of Panamint Springs on the north side of State Highway 190 immediately west of the junction with the gravel road leading to Darwin Falls (Panamint Butte Quadrangle, 1951 edition). A section was measured here. Pollens from top of section and directly under the basalt in sandstone and gritty moderately well-bedded, coarse to fine, poorly sorted gray to tan sandstone, with numerous pebbly lenses, baked red at upper contact. Flora from red-baked finer sandstone 2 feet below basalt.

The 18 species representing this florule were secured from samples taken at the top of the section directly under the basalt. Recovered ere 5 pines (including Colter, Jeffrey and Ponderosa); two walnuts; one Typha, one Castanopsis; two oaks; one elm; one Ribes; one Holodiscus; one Fremontia; one Garrya; one dogwood; and one ash. 45 pollen grains were studied.

This flora, from a region now desert, represents an assemblage much like those which can be observed today in the forest woodland ecotone of southern California and bordering regions. Members of the yellow pine forest represented at Panamint Spring include P. ponderosa, P. jeffreyi, Quercus kelloggii, Ribes cereum, and Cornus nuttallii. These species often mingle with P. coulteri, P. tuberculata, Quercus wislizeni, and Garrya sp. in the mountains of southern California. ( a valley oak occurs in this florule, Quercus lobata). Two species in this flora, Juglans rupestris and Ulmus alata, no longer live in this region; they occur in the Central and southwestern United States, areas with both summer and winter precipitation.

With respect to climate, the flora suggests an annual precipitation of approximately 20-25 inches, to judge from weather records at several stations at the lower margins of forest in southern California. By contrast, rainfall at the locality is only 2-3 inches yearly at the present time. Winters appear to have been generally mild, to judge from the fact that the flora includes several species that are in southern California and in regions to the southeast. Low winter temperatures were probably in the range of 40 degrees F and summers probably had extremes not greatly in excess of 90 as compared with 120 degrees F today.

As for the Coso mammalian fauna, it seems desirable to recall that the abundant equids led Schultz (1937) to visualize the region as composed chiefly of extensive grasslands in a semiarid climate. The pollen floras clearly demonstrate, however, that the region was sufficiently moist to support forest. The grasses on which the horses were grazing no doubt were common in meadows on the margins of small lakes and ponds. In addition, it seems probable that grasses were scattered through openings in the forest, and within the forest itself. The former relations still exist near the lower margin of the Sierran pine forest where it interfingers with the oak-savaana community, and the latter can be see today in relict areas where the virgin pine community persists in the Sierra Nevada. The horses were probably living under similar conditions east of the low Sierra Nevada in Late Pliocene, not in a semiarid grassland country well removed from forest.

The samples chosen for study were in all cases selected from the finest-grained sediments available in the different sections examined, and from the darker-colored strata owing to the their higher organic content. Since not all the sections examined contain very fine clay to silt-size sediments, we have had to deal with some medium and even coarse-grained sediments. Actually, there seemed to be little relationship between the spore-pollen yield and the grain size of the rock. Some of our richest samples were recovered from coarse, hard sediments. From the samples collected, we have prepared more than 500 residues by the procedures described below, and have studied more than 1,200 slides. All slides with fossil spores and pollen were preserved for future reference and were mounted either with diaphane or gelatin.

The following procedures were employed in the preparation of the samples, either in whole or in part.

1. HCL treatment. Powder sample, soak in concentrated HCL and either (a) heat to boiling point over a water bath, or (b) leave in acid for 1-4 days. Centrifuge, decant the supernatal liquid, washing with distilled water 4 or 5 times.

2. HFL treatment. Pour HFL (technical grade) carefully in small quantities into a polyethyl receptacle containing the sample already treated by procedure 1. Then (a) leave it in acid for 1-3 days or (b) for longer periods, such as a month, or (c) heat over a water bath in a closed hood for immediate use. Washing must be very thorough, using distilled water 4-5 times, followed by absolute alcohol.

3. Acetolysis (a) dehydrate sample by washing with absolute alcohol, (b) add 5 or 10cc acetic anhydrid, (c) add 5 to 10 drops--drop by drop--concentrated sulfuric acid, (d) heat over water bath to 100 degrees C, stir, leave in bath for a few minutes (keep the same time interval in every case, as length of time may affect the size of the grains), (e) centrifuge, decant supernatal fluid, thoroughly wash with distilled water (add carefully), followed by a wash in absolute alcohol. In this procedure use only heavy-duty glass centrifuge tubes.

4. Heavy liquid separation (a) Add enough Bromoform (sp. gi 2) to have the sample float in the liquid. (b) Stir sample thoroughly, breaking up any lumps, (c) centrifuge at high speed (1,300-2,500 rpm) using polyethylene tubes (glass may break), (d) poor liquid into a funnel fitted with a stopper at the bottom (e) let stand for 20 minutes so that the grains will rise toward the surface, then drain off the bottom part of the fluid, (f) drain off remaining liquid into test tube, dilute with a absolute alcohol, centrifuge and decant the liquid. Residue will contain microfossils, if any.

It is not necessary to employ all of the above procedures or to follow them in the order described. Procedure 1 may be omitted if the sample has only a low calcium content. Procedure 3 may not be needed for samples of low organic content, and it may be carried out before procedure 2 or after procedure 4.

There are also a few alternative methods which we have used, with some success.

1. An ultrasonic bath can be used for speedy disintegration of samples in HF, provided the container is safely sealed. The time required is 5-10 minutes.

2. Soak samples in absolute alcohol; strain sediments with a 200-mesh blotting cloth; centrifuge and decant the liquid. Process under procedure 4. This eliminates procedures 1 and 2. Its chief use is in fine, poorly compacted sediment, and for quick inspection of the sample.

3. Samples soaked in HF, as in procedure 2, can be strained by a fine-meshed sieve (200 mesh, metal or blotting cloth made of natural fibers) before centrifuging. This eliminates the greater bulk of undigested sediments and chemical precipitates.

Chemical effects: The dimensions of a fossil grain treated by HCL and HF, even though following by acetolysis, will be smaller than fresh grains treated by acetolysis. The longer the time a grain is under chemical treatment, the greater will be the effect. Some pollens are not resistant to chemical treatment and are therefore not represented in the final samples. Of particular importance to the present problem are the grains of Populus and Umbellularia, genera that might well be expected in some or possibly all of our floras, but have not been found (Umbellularia) or else are quite rare (Populus). Since most spores and pollens are resistant to acid, the exine sculpture and the structure of the grains are not affected by chemical treatment. However, grains from sandy samples after passing through repeated stirring and centrifuging may be abraded sufficiently by the sand so that diagnostic characters are lost; if long continued, only miscellaneous bits of tissue remain.

We have not found any observable differences in the morphology of our fossils and Recent grains. Mounting with gelatin seems superb, although it sets immediately.