CONTENTS.

Introduction[1]
Geographical Characteristics of Algeria[2]
Climate of Algeria[6]
Some Characteristics of the Vegetation of theTell[15]
The Forests of Algeria[18]
The High Plateau[20]
Boghari to Laghouat[20]
Djelfa to Laghouat[22]
Laghouat[23]
The Oasis of Laghouat[24]
The Plain[25]
The Dunes near Laghouat[27]
The Mountains about Laghouat[28]
Effects of Grazing on Vegetation near Laghouat[29]
From Laghouat to Ghardaia[31]
Region of the Dayas[31]
Daya of Tilrempt[32]
The Chebka[34]
Ghardaia[36]
The Oasis of Ghardaia[38]
The Plain (Hamada) of Ghardaia[39]
The Mountains about Ghardaia[41]
The Valley of the M’Zab[41]
Protected Areas near Ghardaia[42]
Root-Habits in the Ghardaia Region[44]
Leaf-Habits in the Ghardaia Region[49]
Growth and Flowering Habits in the Ghardaia Region[49]
Ghardaia to Touggourt[50]
Ghardaia to Ouargla—Vegetation[53]
Ouargla to Touggourt—Vegetation[56]
Touggourt to Biskra—Physical Features andVegetation[58]
The Biskra Region[59]
Topography[59]
Plant Habitats of the Biskra Region[60]
Vegetation of the Biskra Region[61]
General Summary and Conclusions[66]
The Environmental Conditions of Plants in Arid Regions[66]
Environmental Features of the Flora of Algeria[69]
Some Effects of Temperature and Rainfall in SouthernAlgeria[71]
The Soil Relation in Southern Algeria[73]
Root-Characters and Species Distribution in SouthernAlgeria[76]
The Biotic Factor[77]
Comparison of Some General Features of the Vegetation ofSouthern Algeria and of Southern Arizona[79]

LIST OF ILLUSTRATIONS.

[Plate A]. Outline map of Algeria, showing main features of surface drainage.
Pl.1,fig.[1.] View of the oasis of Laghouat.
[2.] Wood market at Laghouat. Juniper, oak, pine, and other kinds of wood, each bunch a camel load, exposed for sale.
[3.] Wood market at Laghouat. Roots of Zizyphus, branches of juniper and pine, and pine bark. The latter is said to be used for staining.
Pl.2,fig.[4.] Shoot-habit of Acanthyllis tragacanthoides. Laghouat.
[5.] Shoot-habit of Zollikoferia spinosa. Laghouat.
[6.] Acanthyllis tragacanthoides on sandy plain. Laghouat.
[7.] Zollikoferia spinosa in habitat, plain (hamada). Laghouat.
Pl.3,fig.[8.] Detail of north slope of Nomad Mountains, where Zollikoferia spinosa is the dominant species. Laghouat.
[9.] Vegetation of plain (hamada) at Tilrempt. The conspicuous shrub is Haloxylon articulatum.
[10.] The daya of Tilrempt from the plain, showing the character of the depression.
Pl.4,fig.[11.] Near view of the daya of Tilrempt. The fortified stage station, bordj, and a nomad camp are to be seen. The flattened, level, lower surface of the trees is the effect of grazing, mainly by camels.
[12.] Jujube (Zizyphus) shrubs and betoum (Pistacia) at the daya of Tilrempt.
Pl.5,fig.[13.] A young specimen of betoum in the midst of a protecting jujube at the daya of Tilrempt.
[14.] Leaf and shoot habit of the jujube (Zizyphus lotus). Daya of Tilrempt.
[15.] Leaves of the betoum (Pistacia atlantica) from the daya of Tilrempt.
Pl.6,fig.[16.] South wall of the valley of the Oued M’Zab at Ghardaia.
[17.] Detail of an eroded bank of the Oued M’Zab at Ghardaia. The overhanging stratum is hardpan similar to the “caliche” of southwestern United States.
Pl.7,fig.[18.] Shoot-habit of Haloxylon articulatum, from the plain near the daya of Tilrempt.
[19.] Agriculture at Ghardaia. The fields are divided into plots about 3 by 4 feet in size, for the more economical use of water. Young barley is shown growing (November).
Pl.8,fig.[20.] Vegetation in upper part of a “draw” on plain north of the M’Zab Valley, Ghardaia.
[21.] Situation of square No. 2, on plain north of valley at Ghardaia.
Pl.9,fig.[22.] Capparis spinosa at base of valley wall at Ghardaia.
[23.] Leaves of Capparis spinosa from Ghardaia.
Pl.10,fig.[24.] Leaf-habit of Dæmia cordata. Ghardaia.
[25.] Shoot-habit of Salvia ægyptica. Ghardaia.
[26.] Upper surface of rocks, showing small incrusting lichens, on a low mountain about 5 km. north of M’Zab Valley, Ghardaia.
Pl.11,fig.[27.] Habitat of Peganum harmala, at Melika, Ghardaia.
[28.] Shoot and leaf habit of Peganum harmala, from Ghardaia.
Pl.12,fig.[29.] Habit of Henophyton deserti at Ghardaia when growing in a protected situation (cemetery).
[30.] Leaf-habit of Henophyton deserti. Ghardaia.
Pl.13,fig.[31.] View in a cemetery at Ghardaia, to show the relatively abundant vegetation.
[32.] View in an M’Zabite cemetery, Ghardaia. Haloxylon articulatum is the leading species shown.
Pl.14,fig.[33.] Habit of Deverra scoparia, from plain about 3 km. north of M’Zab Valley, Ghardaia.
[34.] Root-habit of Gymnocarpos fruticosum, from plain about 3 km. north of M’Zab Valley at Ghardaia.
Pl.15,fig.[35.] Root-habit of a mature specimen of Peganum harmala, from the floor of the M’Zab Valley near Ghardaia. The soil at the place is comparatively deep.
Pl.15,fig.[36.] Root-systems of Helianthemum sessiliflorum (right), Haloxylon articulatum, and Nolletia chrysocomoides (left), from the flood-plain of the Oued M’Zab, Ghardaia.
Pl.16,fig.[37.] Shoot and root habit of Citrullus colocynthis. Oued M’Zab, Ghardaia.
[38.] Euphorbia guyoniana, in the valley of the Oued M’Zab at Ghardaia.
Pl.17,fig.[39.] Habit of Euphorbia guyoniana. Ghardaia.
[40.] To the left, shoot of Centaurea sp., showing effect of grazing; to the right, shoots of Teucrium pseudo-chamæpitys. From Ghardaia.
Pl.18,fig.[41.] Habit of Salsola sp. (below) and Echinopsilon muricatus, from the M’Zab Valley, Ghardaia.
[42.] Ghardaia to Ouargla. View overlooking the hamada about 28 km. from Ghardaia. The relatively abundant vegetation is associated with a light cover of sand over the area shown. The leading species are Aristida, Deverra, and Haloxylon.
Pl.19,fig.[43.] Retama retam, in dunes about 58 km. from Ghardaia.
[44.] Dates at the Bordj Zolfana, about 58 km. from Ghardaia—one of two wells encountered between Ghardaia and Ouargla.
[45.] Ghardaia to Ouargla. View overlooking flood-plain of the Oued M’Zab, or a tributary of this oued. The adjacent upland is apparently without plant life.
Pl.20,fig.[46.] Vegetation on edge of the Oued M’Zab, about 63 km. east of Ghardaia, showing habitat of Rhantherium adpressum in foreground.
[47.] Sandy flood-plain of the Oued M’Zab, about 63 km. from Ghardaia. Retama, Genista, and Ephedra are the leading plants in this place.
[48.] Habit of Ephedra alata in habitat shown in figure 47. This specimen was 1.5 m. high.
Pl.21,fig.[49.] View of habitat of Ephedra alenda, 138 km. from Ghardaia.
[50.] Detail of suckering habit of Ephedra alenda, from habitat shown in figure 49.
Pl.22,fig.[51.] Vegetation, mainly Ephedra and Retama, of the western edge of the Chott Mellala.
[52.] Approach to western edge of the Chott Mellala, showing characteristic rounded hills, or mamelons.
Pl.23,fig.[53.] View between the Ouargla plain and the Chott Mellala, showing characteristic appearance of eroded hills.
[54.] Looking toward the Ouargla plain (reg).
[55.] Shallow well about 25 km. north of Ouargla.
Pl.24,fig.[56.] Ouargla to Touggourt. Leaf-habit of Limoniastrum guyonianum. The surface of the leaves is covered with an incrustation of salts.
[57.] Habit of Limoniastrum guyonianum. About 25 km. north of Ouargla.
Pl.25,fig.[58.] Vegetation of the reg desert, about 25 km. north of Ouargla. Ephedra and Retama are the leading species of the area—a spreading dune.
[59.] Shoot-habit of Halocnemon strobilaceum. About 28 km. north of Ouargla.
Pl.26,fig.[60.] Habit of Halocnemon strobilaceum on the edge of a chott, about 28 km. north of Ouargla.
[61.] Shoot and leaf habit of Anabasis articulata, about 32 km. north of Ouargla.
Pl.27,fig.[62.] Detail of the shoot-habit of Salsola tetragona?, about 25 km. north of Ouargla.
[63.] Habit of Nolletia chrysocomoides near the edge of a chott, about 80 km. north of Ouargla.
Pl.28,fig.[64.] Tamarix sp. as a sand-binder near Bled-el-Amar, south of Touggourt.
[65.] Biskra. Habitat of Euphorbia guyoniana, looking toward the Djebel Maouya, with the Chaine de Sfa in the background.
Pl.29,fig.[66.] Characteristic vegetation on the north slope of the Djebel Bou Rhezal, Biskra. Haloxylon scoparium is a prominent species.
[67.] North base of Ed Delouatt hills, west of Biskra, showing the low facing dunes. To the right is a glimpse of an oued which pierces the hills in the middle distance.
Pl.30,fig.[68.] Flood-plain of the Oued Hamman es Salahin, Biskra. Halophytes of various species occupy the foreground.
[69.] Habitat of Phelyæa violacea shown in figure 70.
Pl.31,fig.[70.] Young shoots of Phelypæa violacea, at north base of Ed Delouatt hills, Biskra.
[71.] Habit of young specimens of Phelypæa. Except for about 15 cm., plants were buried by sand. Biskra.
Pl.31,fig.[72.] Asphodelus sp. at north base of Ed Delouatt hills, Biskra. Photographed in March.
Pl.32,fig.[73.] Detail of square No. 1, on low hills north of Biskra.
[74.] Vegetation of north slope of the low hills which are north of Biskra. Ferula vesceritensis is the perennial appearing in the figure.
Pl.33,fig.[75.] Detail of square No. 2, near area shown in fig. 74. Ferula and Haloxylon are leading species.
[76.] Root-habit of Haloxylon scoparium, from a wash near Biskra.
[77.] Young shoots and mature roots of Ferula vesceritensis. North of Biskra.
Pl.34,fig.[78.] Root-habit of Fagonia growing on edge of a wash. Biskra.
[79.] Large lateral root of Haloxylon, with numerous deciduous rootlets, no longer functional.
[80.] Shoot-habit, taken from above, of Fagonia from the flood-plain of a small oued near Biskra.
Pl.35,fig.[81.] Spring annuals, March 17, on north slope of the Djebel Bou Rhezal, Biskra.
[82.] Root and shoot habit of Peganum harmala, Biskra. The main root is especially well developed, although the species has a generalized root-system.
Pl.36,fig.[83.] Annuals growing with Peganum, near Biskra.
[84.] General view of the north face of the Djebel Bou Rhezal, Biskra. Apparently barren, plants are rather numerous in the rock crevices and small washes of the mountains.

BOTANICAL FEATURES OF THE ALGERIAN SAHARA.